600284040
February 1984
PBSiJ-155225
GEOTECHNICAL QUALITY ASSURANCE OF CONSTRUCTION OF
DISPOSAL FACILITIES
by
S. J. Spigolon and M. F. Kelley
Geotechnical Laboratory
U.S. Army Engineer Waterways Experiment Station
Vicksburg, MS 39180
Interagency Agreement No. AD-96-F-2-A077
Project Officer
Robert Landreth
Solid and Hazardous Waste Research Division
Municipal Environmental Research Laboratory
Cincinnati, Ohio 45268
MUNICIPAL ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
• CINCINNATI, OHIO 45268
REPRODUCED BY
NATIONAL TECHNICAL
INFORMATION SERVICE
U.S. DEPASTIKNT OF COMMERCE
SPRINGFIELD, VA. 22161
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing)
REPORT NO.
_. EPA-6QQ/2-84-040
3. RECIPIENT'S ACCESSION NO.
PR* L 1 5 5 9 9
TITLE AND SUBTITLE
GEOTECHNICAL QUALITY ASSURANCE OF CONSTRUCTION
OF DISPOSAL FACILITIES
p. REPORT DATE
February M984
6. PERFORMING ORGANIZATION CODE
AUTHOR(S)
8. PERFORMING ORGANIZATION REPORT NO.
S. J. Spigolon and M. F. Kelley
PERFORMING ORGANIZATION NAME ANO AOORESS
Geotechnical Laboratory
U.S. Army Engineer Waterways Experiment Sta.ti.on
Box 631
Vicksburg, 'MS 39180
10. PROGRAM ELEMENT NO.
BRD1A
11. CONTRACT/GRANT NO.
AD-96-F-2-AQ77
2. SPONSOHING AGENCY NAME ANO AOORESS
Municipal Environmental Research Laboratory-Cirr. ,OH
Office of Research and Development
U.S. Environmental Protection Agency
Cincinnati, Ohio 45268
13. TYPE OF REPORT ANO PERIOD COVERED
.Final 4/82 - 12/82
14. SPONSORING AGENCY COO6
EPA/6QQ/14
19. SUPPLEMENTARY NOTES
Contact Project Officer: Robert E. Landreth 513/684-7871
6. ABSTRACT
This report presents four major topics related to the permittee's responsibilities
during construction, operation, and closure of a hazardous waste disposal facility:
(1) geotechnical parameters that should be tested and/or observed, (2) selection of.
sampling methods and sample sizes for the geotechnical parameters, (3) laboratory and
field testing methods for investigating geotechnical parameters, and (4) a quality
assurance program suited to the unique responsibilities of the permittee.
The purpose of the report is to provide technical background for use by
permittees, designers, specifiers, quality assurance engineers, and permit writers for
hazardous waste.disposal facilities. The document addresses the quality control
aspects of construction, operation, and closure of a hazardous waste disposal facility
(it is assumed that the quality aspects of site selection, characterization, and
design have already been managed). Types of facilities covered by the report include
landfills, surface impoundments, waste piles, and land treatment units.
This report was submitted in fulfillment of Interagency Agreement No.
AD-96-F-2-A077 by the U.S. Army Waterways Experiment Station in cooperation with the
U.S. Environmental Protection Agency. The report covers the period April to December
1982, when work was completed.
17.
KEY WORDS ANO DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
COS ATI Field/Group
18. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS fTlul Rlpor
UNCLASSIFIED
21. NO. OF PAGES
19.3.
20. SECURITY CLASS i Thu ptftl
UNCLASSIFIED
22. PRICE
EPA f»mi 2220-1 ;R»». 4-77) Previous COITION i* OMOLCTC
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DISCLAIMER
The information in this document has been funded wholly or in part by
the United States Environmental Protection Agency under assistance agreement
number AD-96-F-2-A077 to the U.S. Army Engineer Waterways Experiment Station.
It has been subject to the Agency's peer and administrative review, and it
has been approved for publication as an EPA document. Mention of trade names
or commercial products does not constitute endorsement or recommendation for
use.
ii
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FOREWORD
The U.S. Environmental Protection Agency was created because of increas-
ing public and government concern about the dangers of pollution to the health
and welfare of the American people. Noxious air, foul water, and spoiled
land are tragic testimonies to the deterioration of our natural environment.
The complexity of that environment and the interplay of its components require
a concentrated and integrated attack on the problem.
Research and development is that necessary first step in problem solu-
tion, and it involves defining the problem, measuring its impact, and search-
ing for solutions. The Municipal Environmental Research Laboratory develops
new and improved technology and systems to prevent, treat, and manage waste-
water and solid and hazardous waste pollutant discharges from municipal and
community sources, to preserve and treat public drinking water supplies, and
to minimize the adverse economic, social, health, and aesthetic effects of
pollution. This publication is one of the products of that research and is a
most vital communications link between the researcher and the user community.
The protection of human health and the environment requires that research
be conducted to determine the manner in which hazardous waste disposal facili-
ties should be constructed. This study is intended to provide technical back-
ground on hazardous waste disposal facility construction for use by designers,
specifiers, -quality assurance engineers and permit writers. The study ad-
dresses the subject of quality assurance of site geotechnical parameters dur-
ing the construction, operation, and closure of landfills, surface impound-
ments, waste piles, and land treatment units.
Francis T. Mayo
Director
Municipal Environmental Research
Laboratory
iii
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ABSTRACT
This report presents four major topics related to the permittee's
responsibilities during construction, operation, and closure of a hazardous
waste disposal facility: (1) Geotechnical parameters that should be tested
and/or observed, (2) selection of sampling methods and sample sizes for the
geotechnical parameters, (3) laboratory and field testing methods for investi-
gating geotechnical parameters, and (4) a quality assurance program suited
to the unique responsibilities of the permittee.
The purpose of the report is to provide technical background for use by
permittees, designers, specifiers, quality assurance engineers, and permit
writers for hazardous waste disposal facilities. The document addresses the
quality control aspects of construction, operation, and closure of a hazardous
waste disposal facility (it is assumed that the quality aspects of site selec-
tion, characterization, and design have already been managed). Types of
facilities covered by the report include landfills, surface impoundments,
waste piles, and land treatment units.
This report was submitted in fulfillment of Interagency Agreement
No. AD-96-F-2-A077 by the U.S. Army Waterways Experiment Station in coopera-
tion with the U.S. Environmental Protection Agency. The report covers the
period April to December 1982, when work was completed.
iv
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CONTENTS
Foreword iii
Abstract iv
Figures vi
Tables - vii
Acknowledgments viii
1. Introduction ........ 1
2. Geotechnical Parameters ... 8
3. Sampling Methods and Selection of Sample Size 32
4. Testing 60
5. The Quality Assurance Program 96
6. Summary 105
References ....... 1Q9
Appendices
A. Glossary of Terms 116
B. Test Method Descriptions 122
v
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FIGURES
Number
1 Relationship between site media and disposal unit at
disposal facility ............... 6
2 Weight-volume relationships . . .......... 16
3 Typical grain-size distribution curves for soils ........ 18
4 Relationship of Atterberg limits to water content . . . . . I . . 20
5 Typical density-water content relationships for compacted
soils ................ 23
6 Example of graphical solution of relative density
relationship ...... ...... 24
7 Results of compacted fill tests, Degray Dam, Caddo River,
Arkansas (Strohm and Torreys 1982) .............. 36
8 Fill water content variability, DeGray Dam, Caddo River,
Arkansas (Strohm and Torrey, 1982) .. ............ 37
9 Fill density variability, DeGray Dam, Caddo River,
in
11
i?
13
Arkansas (Strohm and Torrey, 1982) .............
Concepts of regression analysis ................
Graphic representation of important values for the authors '
recommended method ......... .
Graphic representation of the solution of BS .........
The Quality Assurance Program .................
38
56
68
71
VI
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TABLES
Number Page
1 Unified Soil Classification System . . . 19
2 Determination of the Consistency of Clays 22
3 Variability of Natural Soil Deposits .... 35
4 t-Factors for Large Samples .................. 51
vn
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ACKNOWLEDGMENTS
This report was prepared by the Geotechnical Laboratory (GL) of the.
U.S. Army Engineer Waterways Experiment Station (WES). The authors of the re-
port were Dr. S. J. Spigolon and CPT M. F. Kelley. Investigation team members
providing technical advice were H. V. Johnson, Jr., and P. G. Tucker. The work
was conducted under the direct supervision of G. B. Mitchell, Chief, Engineer-
ing Group, Soil Mechanics Division, GL, and the general supervision of C. L.
McAnear, Chief, Soil Mechanics Division, GL, 'and Dr. W. F. Marcuson, III, Chief,
GL. COL Tilford C. Creel was Commander and Director of WES during preparation
of this report. Mr. Fred R. Brown was the Technical Director.
viii
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SECTION 1
INTRODUCTION
The U.S. Environmental Protection Agency (EPA) issued its interim final
rules and regulations for hazardous waste disposal facilities in the Federal
Register, on July 26, 1982 (E.P.A., 1982). As stated in the preamble, "EPA
wants to make sure that the issuance of a RCRA (Resource Conservation and
Recovery Act) permit for a facility means that a certain level of protection
is provided and that the public can be assured* that the prescribed level of
protection will be achieved."
Also in the preamble, "Section 3004 of RCRA provides that EPA has
authority to issue regulations covering owners or operators of (hazardous
waste) treatment, storage and disposal facilities as may be necessary to
protect human health and the environment." Given this authority, the EPA
has charted a defense strategy with two basic elements. The "first line of
defense" calls for facility design and operating standards that prevent
groundwater contamination by controlling the source of contamination. The
"second line of defense" is a groundwater monitoring and response program
designed to remove leachate from the groundwater if it is detected.
The EPA believes that adequate protection will be afforded if hazardous
waste disposal facilities meet both (a) the technical performance standards
and (b) the environmental performance standards promulgated to execute their
two element defense strategy. A quality assurance program for the construc-
tion, operation, and closure of a hazardous waste disposal facility, though
not required by the current regulations, is mandated in EPA policy and is a
management practice which can assure that these standards are met, that the
strategy is executed, and that human health and the environment are protected.
THE TOTAL QUALITY SYSTEM
Quality is defined (Lester, Enrick and Mattley, 1977) as the level of
performance of a material, product, or process, measured in terms of speci-
fied requirements. In construction, the total quality system, as described
by Abdun-Nur (1963), Willenbrock (1976), and others, contains several sub-
systems: Planning, Design, Plans and Specifications, Construction, and
Monitoring. The purpose of these activities is to insure that quality is
what it should be.
* Underline emphasis is that of the authors.
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Planning establishes the quality level that is desired. For a disposal
facility, planning begins with the Environmental Protection Agency. The
agency interprets the needs of society and promulgates rules and regulations.
These rules and regulations establish levels of quality that the EPA recog-
nizes as necessary and sufficient to protect the human health and environment.
In the design subsystem, an analysis is made of available resources. The
desired quality levels are fixed in terms of what is to be required at the
specific site, based on site characterization and other studies.
In the plans and specifications subsystem, the requirements of the de-
sign are translated into specific instructions for achieving the required
quality levels. Methods for evaluating the quality of construction, and the
acceptable level of quality as defined by these methods are integral parts
of the specifications.
The construction subsystem for a disposal facility includes initial con-
struction, operation, and closure. Construction transforms the designed
facility into reality, and quality becomes physically real. Quality assurance
activities within the construction subsystem include (a) process control and
(b) acceptance sampling and testing. (See Construction Quality Assurance,
later in this section.)
Finally, monitoring of the behavior of the completed disposal facility
should provide data of how the facility actually performs. By closing the
quality loops, monitored performance data can be used by EPA in the planning
stage of future projects to review its desired, and mandated, quality levels.
PURPOSE OF REPORT
This study report is intended to provide technical background for use by
designers, specifiers, quality assurance engineers, and permit writers. It is
directed only to that part of the total quality system (Abdun-Nur, 1963) that
encompasses quality assurance during the construction, operation, and closure
of a hazardous waste disposal facility. This report does not address the
design of a hazardous waste disposal facility. Hence, no guidance for the
quality levels of disposal facility site selection, site characterization or
design is included in the report.
The technical background presented in this report is aimed at the per-
mitting requirements that deal with quality assurance. It specifically treats
the subject of quality assurance of site geotechnical parameters during con-
struction, operation, and closure of:
a. Landfills (burial sites)
b. Surface impoundments
c. Waste piles
d. Land treatment units
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It does not address injection wells or seepage facilities.
This report is not intended to be a textbook that teaches the funda-
mentals of soil mechanics, soils testing, or statistical methods to those
engineers responsible for the geotechnical design and/or construction of a
disposal facility. Rather, this report should provide both specialists and
nonspecialists involved in the design or evaluation of design (permit review)
with a common basis for understanding of the topics discussed. The informa-
tion provided summarizes each topic, presents the most pertinent features of
each, and provides terminology, definitions, equations, applications, and
literature references. For further study, or to acquire an in-depth under-
standing of the various topics, the reader is referred to the several text-
books on each topic.
SCOPE OF THE REPORT
During the construction, operation, and closure of a hazardous waste
disposal facility, the permittee (owner or operator) has the responsibility to
test and/or observe and to document:
a. The verification of (a) geologic media site characterization and
(b) soil engineering properties design assumptions following the
exposure of trench or impoundment walls and bottoms
b. The quality of geotechnical construction, involving materials and
workmanship, for compliance with specification and permit
requirements
This document discusses four major topics related to the geotechnical
quality assurance responsibilities of the permittee during the construction,
operation, and closure of a disposal facility:
a. In Section 2, those geotechnical parameters that should be tested
and/or observed and documented are identified and described. The
reasoning for their selection is given. Tests and/or observations
used for construction process control are often different than those
used for site media verification or for acceptance evaluations.
b. In Section 3, sampling and frequency of testing for the geotechnical
parameters are discussed. The discussion is based on statistical
methodology and includes sampling plans, selection of sample size,
and calibration of test equipment.
c. In Section 4, the commonly used laboratory and field testing and/or
observation methods, needed for investigation of the geotechnical
parameters defined in Section 2, are identified and described. A
discussion of merits and limitations of the various methods is given.
Criteria are proposed for selection among alternative test methods.
d. In Section 5, a quality assurance program, suited to the unique con-
struction responsibilities of the permittee, is presented and
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discussed. The documentation necessary to provide a valid record of
the quality of the work is recommended.
The report is limited to consideration of geotechnical tests and/or ob-
servations, i.e., involving physical properties of soils. Geochemical and
geohydrologic tests such as soil pH, ion exchange capacity, pore water age,
or infiltration capacity, are not included. It is uncommon in the earth-
work construction industry to perform geochemical or geohydrologic tests as
part of quality control of construction. But if such tests are deemed neces,-
sary by the permittee's forces during construction, they certainly should be
performed on an as-needed basis. An example is the need to verify an engi-
neering property assumption made during the design stage on the existing
soils in a newly accessible part of the site.
Although this report is restricted to geotechnical parameters, most of
the concepts of sampling inspection, quality control, and documentation apply
equally well to site characterization studies, geochemical or geohydrologic
studies, monitoring, and other site activities not addressed.
CONSTRUCTION QUALITY ASSURANCE
Willenbrock and Shepard (1980) have compared Quality Assurance/Quality
Control (QA/QC) Systems within the civilian construction industry. Included
are (a) highway construction, (b) nuclear power plant construction, (c) U. So
Navy and U. S. Army Corps of Engineers facilities construction, and (d) build-
ing construction by private or public owners. In most areas of construction,
including highway, Navy, Army, and buildings, there is a contractual relation-
ship between the owner (whether public or private) and the contractor. The
owner's design representative prepares plans and specifications. The contrac-
tor is expected to use those control of quality, or process control, proce-
dures that are necessary to control his materials and workmanship to comply
with the plans and specifications. The owner's inspectors perform those
acceptance sampling and testing functions needed to give confidence to the
owner that the materials provided and the work performed are acceptable. Thus
three distinct quality groups, responsibilities, and procedures, result in a
near adversary relationship between the owner and the contractor.
This near adversary relationship can be illustrated by typical earthwork
specifications (Soil Conservation Service, 1973) which state, "These tests
performed by the Engineer will be used to verify that the fills conform to
the requirements of the specifications. Such tests are not intended to
provide the Contractor with the information required by him for the proper
execution of the work and their performance shall not relieve the Contractor
of the necessity to perform tests for that purpose."
EPA policy creates a unique construction situation by vesting the respon-
sibility for all aspects of quality assurance with the permittee (EPA, 1982).
This is similar to the policy of the U. S. Nuclear Regulatory Commission as
given in 10 CFR 61.12 (NRC, 1982). The NRG applies this policy to the li-
censee for nuclear power plant construction and to the licensee of a low-level
radioactive waste disposal site. However, the major turnkey contractor for a
nuclear power plant must deal with numerous subcontractors and materials
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suppliers, thereby creating the same near adversary situation as in other
civilian construction.
The permittee of a hazardous waste disposal facility is therefore some-
what unique in the construction industry in that he is totally responsible,
to the regulatory agency, for the facility's (a) site selection, characteriza-
tion, and design, (b) construction, operations, and closure, and (c) quality
assurance activities, including process control, acceptance sampling and
testing, and documentation of the quality assurance program. That he is re-
sponsible for both construction and its inspection poses a potential conflict
of interest. The quality assurance program presented in Section 5 of this
report accounts for the permittee's unique situation and this potential con-
flict of interest.
During the life of a disposal facility, the permittee will have three
major functions within his construction responsibilities:
a. The Design Function: This function includes all pre-permit activity,
such as site selection, site characterization, analysis and design,
plans and specifications, and preparation of the permit application.
Post-permit activities include verification of design conditions for
exposed site media (see Figure 1) and critical evaluation of inspec-
tion reports.
b. The Construction and Operations Function: This function includes
provision of all materials (including off-site materials) and work-
manship during construction; i.e. to include all materials and work-
manship involved in site preparation, trench excavation, and the
placement of liners, embankments, leachate' collection systems,
intermediate covers, and final covers.
c. The. Inspection Function: This function includes the sampling,
testing and/or observation, initiation of corrective action for
instances of non-acceptance, and documentation of all the post-permit
construction work. The inspection function involves all the mate-
rials provided by, and all the workmanship of, the permittee as part
of his construction and operations function.
Discussion of the organizational structure by which the permittee may
accomplish these functions is contained in Section 5 of this report. The
permittee may use in-house forces or external contract forces, or any combi-
nation of the two. It is inevitable that the permittee's forces responsible
for the design and inspection functions will have different attitudes, con-
cerns , and responsibilities than the forces responsible for the construction
and operations function. Therefore, it is essential that each of these
separate forces report directly to the permittee's top level management rather
than for any one group to be subordinate to another.
It is the permittee's inspection function that is of particular concern.
Unlike other parts of the construction industry, the permittee of a hazardous
waste disposal facility is responsible for both construction process control
and owner acceptance sampling and testing. During construction the permittee
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COVER OR CAP
DISPOSAL
UNIT
CTRENCH)
^LINER
V K V\
SITE MEDIA
Figure 1. Relationship between site media and disposal unit
at disposal facility
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can fulfill these two responsibilities synergistically. That is, the feedback
from observations and from acceptance sampling and testing can frequently be
used to control the construction process to provide the specified level of
quality by indicating the corrective measures to be taken.
Although the permit requirements and the construction specifications,
prepared as part of the permittee's design function, will normally specify
performance or end-result standards, the permittee's process control of his
men, machinery, and materials will more likely be by method, or recipe,
specifications.
Because of the somewhat unique permittee-regulatory agency relationship,
the need for complete inspection documentation is critical. This need in-
cludes not only the documentation of acceptance tests and observations made
to establish compliance with the specifications, but also (a) the verification
of geologic media site characterization and engineering soils properties
design assumptions following the exposure of walls and bottoms of disposal
units, and (b) observations and tests made as part of the permittee's process
control of materials and workmanship. Critical interpretation of the observa-
tions and tests by competent, knowledgeable, experienced and qualified per-
sonnel, responsible to the permittee, is also essential. This complete
recording, review, and acceptance of inspection observations and tests will
then serve (a) to provide the regulatory agency with confidence in the quality
assurance program, and (b) to provide a basis-in-fact in the event of future
problems and/or litigation.
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SECTION 2
GEOTECHNICAL PARAMETERS
The permittee is responsible for the quality of all geotechnical mate-
rials and workmanship during the active life of a disposal facility. This
life includes (a) the pre-permit stage: site characterization, analysis,
design, and specification, and (b) the post-permit stage: construction,
operation, and closure. The geotechnical engineering aspects of both phases
require data on the engineering properties of those parts of the soil and rock
formations of the site that influence the project.
The materials to be characterized by engineering properties include:
a. Site media (See Figure 1)
(1) In situ materials, not moved or disturbed
(2) Excavated, transported, manipulated, and processed materials
b. Off-site materials
(1) Nearby natural materials, such as sand from a nearby
" borrow pit
(2) Imported or shipped natural materials, such as bentonite clay
(3) Imported or shipped manufactured materials, including geo-
membranes, geotextiles, Portland cement, and asphalt cement
During the design phase of a disposal facility project, all of the exist-
ing or proposed materials are characterized by their location, dimensions,
and engineering properties. Tests for the engineering properties are diffi-
cult and time consuming. Therefore, during construction the QA inspector
usually uses simpler, more rapidly performed soil tests that are good indi-
cators of the engineering properties in his acceptance evaluation.
The construction process involves control of materials and workmanship.
Materials are tested and/or observed for use in the project prior to their
incorporation. Then construction workmanship is used to process the materials
to their final form. The workmen, their supervisors, and the process inspec-
tor must interact to properly control the process. The tests and/or observa-
tions used to control the process may be one or more of the acceptance tests,
or may be any other test/observation that will directly inform the workman
8
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and/or his immediate supervisor of the necessity for corrective action. The
objective of process control is to direct the work in an efficient manner, to
catch mistakes before or as they occur, to cause the mistakes to be corrected,
and to ultimately produce an acceptable product. The project specifications
usually state only the acceptance/rejection standards.
As an example, the design may require that a clay liner material be com-
pacted so that a given level of imperviousness (low permeability) is achieved
throughout the entire liner. The required level of permeability is defined..
For field use, this is translated into a specified density and water content.
These are usually related to a laboratory compaction test that adjusts the
density and water content requirements for changes in soil texture. Accep-
tance levels are set based on field density and water content tests. The
workman, on the other hand, can control only his processing. Given an accept-
able soil, he and the process control inspector can control lift thickness,
uniformity of lift thickness, water content'(by additional water or by
drying), type and size of roller, number of passes, and uniformity of rolling.
They must then translate these factors into a pattern of work that will re-
sult in acceptable soil density and soil water content which will indicate
that the required low permeability is achieved.
The objective of this section of the report is to identify those geotech-
nical parameters that should be observed or tested and documented during the
construction, operation, and closure of a disposal facility. These are
parameters defined in project specifications for the evaluation and acceptance
of the work. In many instances these will be the same parameters as those
used in the pre-permit stage. Therefore a brief discussion of the pre-permit
stage will introduce the parameters.
PRE-PERMIT STAGE
The investigation of a proposed disposal facility includes geologic
studies, geohydrologic studies, drainage studies, site investigation by
geophysical and test drilling methods, and the sampling and testing of the
site media. Specific details of the techniques for these studies are beyond
the scope of this report. It is assumed that the permittee, in performing his
design function, will employ qualified professionals to perform and evaluate
the work in accordance with established, rational practices. The combination
of subjective geologic studies and geotechnical engineering site investiga-
tions should result in adequate data for the purpose of site characterization
for design.
Geology and Geohydrology
Site characterization studies start with inferences based on site geo-
logic studies. The existing geologic information on the site area is re-
viewed. Studies may include earth satellite photograph interpretation, aerial
photograph interpretation, and field studies including observation of terrain,
natural and man-made cuts, and drainage. Erodibility potential may be in-
cluded in the studies. They are expected to provide evaluations of:
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a. Stratigraphy: The origin of each stratum and its relationship to
adjacent geologic units is inferred. Subsurface irregularities or a
pattern of spatial variation in quality characteristics may be
revealed.
b. Lithology: The soil and rock strata should be characterized on the
basis of mineralogy, texture, fabric, and origin of materials.
c. Structure: Macro(gross)-structure includes bedding attitudes as
well as fracture systems. The latter include faults, cracks, joints,
and slickensides.
d. Ground Water: The presence of aquifers and perched water tables,
including their flow gradients, flow direction, and recharge and
discharge areas, should be defined. Surface drainage should be
established as it affects the dispersal site drainage.
Site Investigation
The subsurface investigation of the immediate site may use geophysical
methods and drilling and sampling. The objective is to define material types
and engineering properties, material zone boundaries, and the spatial and
random variability of engineering properties in each material and zone. Mate-
rial variability is discussed in detail in Section 3 of this report.
Material type and variability are best established by soil index prop-
erties tests on samples from drill holes and test pits. These tests are
relatively inexpensive and easily performed. The drill holes and/or test pits
should be located through a combination of geologic inference and the sampling
methods of Section 3. In this manner, random samples of each stratum can be
used to characterize the classification and variability of the various strata.
Tests for engineering properties require high quality undisturbed
samples (ASTM, 1970). Construction experience has shown that only few projects
can afford the expense of large numbers of such samples and tests. Therefore,
only a sufficient number of engineering properties tests are made, with asso-
ciated index properties tests, to confirm the expected relationships between
the two and to supplement geologic inferences about the soil engineering
properties. This information is extrapolated over the site by means of the
data from the more numerous index properties tests.
The accuracy of the determination of material zone boundaries and the
location of a water table is a function of the number and quality of borings
made. These borings can often be supplemented by geophysical tests which
cover wide areas less expensively than drilling. Thin or discontinuous zones
are easily missed and the interpretations of layer thicknesses are sometimes
affected by the vertical interval between samples. Within the upper 10 to
15 feet of the ground surface, test pits can disclose the total soil profile
over a limited area (i.e. the walls of the pits).
10
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ENGINEERING PROPERTIES TESTS
During the analysis and design phase of the pre-permit stage, the per-
mittee makes estimates of the configuration and engineering properties of the
natural site media. These are based on the geologic and site investigation
studies referre'd to above. The permittee als.o, makes assumptions about the
expected engineering properties of the construction placed materials. This
requires quantitative and specific information on the physical and strength
properties of soils that have direct and valid application to the design .
problem (ASTM, 1970). These properties include permeability, compressibility,
and shear strength (USAE, WES, Appendix A, 1960). Although not considered an
engineering property, the susceptibility of the site soils to erosion (erodi-
bility) by water or air should be estimated in the design phase.
Permeability
The permeability of a soil or other material is a major influence on the
flow of water or other fluids through liners, covers, and leachate collectors.
It also affects the time rate of settlement and the rate at which soils in-
crease strength by consolidation. Drainage of soils, capillarity, and poten-
tial for frost heave are interrelated with permeability. Physical tests
include:
a. Laboratory permeability tests
b. Laboratory capillarity tests
c. Field permeability tests*
d. Field infiltration rate tests
Compressibility
The amount of compression settlement of a soil due to direct loading, and
the time rate at which it will occur, is influenced by soil compressibility.
Of particular interest are the compression of a buried waste under the load of
overlying waste and the cover soils, and the compression of sludge in a sur-
face impoundment. (However, there are currently no well accepted procedures
for determining the compressibility of these materials.) The tendency of a
soil to collapse or to undergo appreciable swell-shrink is related to com-
pressibility. Physical tests include:
a. Laboratory consolidation test
b. Swell and swell pressure tests
Olsen and Daniel (1981) have shown that field permeabilities may be one or
more orders of magnitude greater than laboratory test derived values.
Therefore, it may be appropriate to perform field permeability tests as
part of the design studies or as part of the site media verification during
construction.
11
-------
Shear Strength
The shear strength of the natural soil influences the stability of the
trench excavation and the structure foundations. The strength of compacted
soil affects the behavior of embankments. Shear strength also affects the
trafficability of the site roadways. Physical tests include:
a. Laboratory direct shear
b. Laboratory triaxial compression
c. Laboratory unconfined compression
Limitations of Design Properties Tests
Although the results of these tests would be ideal for quality assurance
inspection during construction, they are not normally performed because they
require (ASTM, 1970; Dept. of Army, 1970; Terzaghi and Peck, 1967):
a. Extensive time: The performance of any of these tests can take from
one full day to as long as two weeks. Efficient control of construc-
tion requires much faster test times.
b. Complex equipment
Co Complex procedures
d. Highly skilled operators
e. Controlled laboratory environment: This often means temperature
control and vibration-free surroundings not normally found at a
construction site.
f. High quality undisturbed samples
Instead, various simpler, faster, index tests, whose results relate to
strength, compressibility and permeability, are performed.
CONSTRUCTION INSPECTION TESTS
Any division of inspection techniques into observations and tests is
necessarily arbitrary. As stated in NCHRP Synthesis 65 (TRB, 1979), "Although
a test is most often thought of as a quantitative measurement of the behavior
of a sample or item, in reality, a test is nothing more than an observation
and can vary from complicated procedures with multiple recordings of data to a
simple notation of appearance." Thus, "Skilled inspectors make tests by ob-
servation because they learn to recognize (material quality by appearance or
behavior during construction operations)."
The purpose of any test or observation is to compare the material used or
the work actually being performed with the desired and/or specified material
and workmanship. Because of the extreme dependence of the regulatory agency
12
-------
on inspection documentation by the permittee for its confidence in the quality
assurance program, it is essential that not only tests but observations be
systematically recorded, even so-called eyeball tests. Also, since observa-
tions are a critical part of the quality assurance program, it becomes imme-
diately obvious that their worth depends on the knowledge, experience and
integrity of the observer.
Criteria for Inspection Tests and Observations
In the construction industry, the constructor's efficient utilization' of
his men, machinery, and materials requires that nearly continuous observations
and tests be made during the progress of the work. Therefore, an observation
or test made as part of the construction inspection program should:
a. Be a good indicator of a design property: That is, it should
correlate well with the appropriate engineering design property
either by itself or in conjunction with other, similar tests.
b. Be accurate and precise: Accuracy is a matter of systematic or
consistent bias and can be improved by calibration. Precision
involves random test variability which should preferably be low
(See Section 3 of this report).
c. Have results quickly available: The test/observation should be capa-
ble of being performed in a time period that will allow an acceptance
decision to be made before the next unit of similar work is begun.
There should be minimal interference with the efficient use of the
permittee's resources of construction personnel and equipment.
d. Be easily performed using simple equipment: The work should require
only minimal technical expertise or training of the inspector/
operator. The equipment should be rugged enough for field laboratory
use, easily maintained, and easily calibrated. The test procedure
must be simple and straightforward, requiring almost no judgement
decisions on the part of the operator.
e. Not require an undisturbed sample, except for density
f. Provide results that are documentable: The test result should be a
number that can be compared to a desired or specified value; ors
it should be a simple, easily understood, consistent, and well
defined descriptive term or phrase.
g. Preferably be nondestructive: The performance of a field test, or
the removal of a sample for laboratory testing, often requires
replacement or patching. This may then result in less than
satisfactory conditions at the sample location.
These criteria are not intended to exclude any special observation or
test. A balance must be maintained between the needs of the permittee for
construction efficiency and the permittee's responsibility to maintain project
quality.
13
-------
Index Properties Tests
In the practice of geotechnical engineering, there has been developed a
small group of laboratory tests called indicator, or index properties, tests.
These are physical tests that generally satisfy the criteria given above for
inspection tests. Some of these tests have been used for similar purposes
for over 50 years.
Taylor (1948) has shown that permeability is a function of grain-size .
distribution, void ratio, degree of saturation, percent clay fraction, .
viscosity of the pore fluid, and the shape and arrangement of the pores. The
shear strength of cohesive soils, according to Whitman (1960), is related to
the void ratio at failure, stress history, structure (flocculated or dis-
persed) , environmental conditions such as the temperature and the nature of
the pore fluid, degree of saturation, conditions at formation of the soil,
capillary tension, mineralogy, and percent clay fraction. Peck, Hanson, and
Thornburn (1974) relate the shear strength of granular soils to relative
density, grain-size distribution, and the shape of the grains. It generally
appears that compressibility and volume stability are related to all of the
relationships for shear strength and for permeability. Erodibility has
empirically been associated with grain-size distribution, percent organic
matter, relative permeability, and void space and pore size.
There exists in the geotechnical engineering literature a large number of
empirical relationships between the engineering design properties described
above and the index properties. Examples of that literature include Peck,
Hanson, and Thornburn (1974), Sowers (1979), Lo (1980), the Navy Design Manual,
NAVFAC DM-7.1 (Dept. of the Navy, 1982), and the Earth Manual (USER, 1974).
Peck, Hanson, and Thornburn (1974) state "If the...tests are properly
chosen, soils or rock materials having similar index properties are likely
to exhibit similar engineering behavior." Also, "In addition to their value
in the correlation of construction experience, they provide a means for check-
ing the correctness of the field identification of a given material. If the
material has been improperly identified, the index properties indicate the
error and lead to correct classification."
The index properties tests useful in an inspection program may be placed
into three categories:
a. Weight-volume relationships
(1) Water content test
(2) Density test
(3) Specific gravity test*
* Usually the specific gravity values established for each soil type during
site characterization are used for calculations during the routine QA
tests. The variability of specific gravity within a woil layer or geo-
logic unit is usually very small. Harr (1977) reports a coefficient of
variation of only 1-4 percent (See Table 3).
14
-------
(4) Calculated values: void ratio, porosity, and degree of
saturation
b. Soil classification tests*
(1) Grain-size distribution tests
(2) Atterberg limits tests
(3) Consistency tests: using simple field methods
(4) Calculated values: plasticity index, liquidity index,
activity, and USCS Classification
c. Laboratory compaction tests
(1) Density/water content/compactive effort tests; for cohesive
soils and "dirty" (i.e. by the USCS those soils classified
as GM, GC, SM, or SC) granular soils
(2) Maximum and minimum density tests; for clean (i.e. by the USCS
those soils classified as GW, GP, SW or SP) granular soils
All of the index properties result from standardized soils tests
(Dept. of Army, 1970; USER Earth Manual, 1974; and ASTM, Pt. 19, 1982). They
are defined as follows:
Natural water content: The natural water content of a soil is defined
as the weight of water in the soil expressed as a percentage of dry weight of
solid matter present in the soil. The water content is based on the loss of
water at an arbitrary drying temperature of 105° to 110°C.
Density: The mass density of a soil material is its weight per unit
volume. The dry density of a soil is defined as the weight of solids con-
tained in the unit volume of the soil and is usually expressed in pounds per
cubic foot. Various weight-volume relationships are presented in Figure 2.
Specific gravity: The specific gravity of the solid constitutents of a
soil is the ratio of the unit weight of the solid constituents to the unit
weight of water.
Void ratio; The void ratio of a soil is calculated as the ratio of
volume of voids to the volume of the soil solids.
Porosity; The porosity of a soil is calculated as the ratio of the volume
of voids to the total volume of soil, which includes air, water, and solids.
* Soil classification by the Unified Soil Classification System (USCS) uses
only grain-size distribution tests for coarse grained soils or Atterberg
limits tests for fine grained soils. Borderline or questionable classi-
fications require both tests.
15
-------
VOLUME
WEIGHT
GAS
WATER
'"/%
^SOLIDS'/!
WATER CONTENT
w =
SPECIFIC GRAVITY
Gs =
VOLUME OF SOLIDS
VOLUME OF VOIDS
VOID RATIO
POROSITY
DEGREE OF SATURATION
UNIT WEIGHT OF WATER
CFRESH WATER)
DRY UNIT WEIGHT
WET UNIT WEIGHT
Vv = V-VS
n =
Vs 1-n
Vv e
V ~ 1 + e
Vw wGs
t
W»
7w = -=. = 62.4 PCF
»w
^s _ "/m
^d V 1 + w
7m =
SUBMERGED (BOUYANT) UNIT WEIGHT 7' = ym - J* =
G.-1
Figure 2. Weight-volume relationships
16
-------
Degree of saturation: The degree of saturation is calculated as the
volume of water as a percentage of the total volume of voids. Thus, at- 100%
saturation, all of the void space is occupied by water, and at 0% saturation,
all of the void space is occupied by air.
Grain-size.distribution; The grain-size distribution of soils is deter-
mined by means of sieves and/or a hydrometer analysis, and the results are
expressed in the form of a cumulative semilog plot of percentage finer versus
grain diameter. Typical grain-size distribution curves are shown in Figure 3.
The' knowledge of particle-size distribution is of particular importance when-
coarse grained soils are involved. Useful values are: (a) the effective
size, which is defined as the grain diameter corresponding to the 10% finer
ordinate on the grain-size curve; (b) the coefficient of uniformity which is
defined as the ratio of the D60 size to the D^ size (Figure 3); (c) the
coefficient of curvature, which is defined as the ratio of the square of the
030 size to the product of the D^Q an
-------
t-1
oo
U S SUndvd Sieve Openings In Inchn U. S Standard Sieve Mumbera
100 3 2 J I 1 * 1 1 4 6 . 10 14 16 20 30 40 SO . 70 100 140
90
80 -
70 -
'C 60 -
.0
>-
"^,
•
10 i i o.s 0.1 0.0$ o.oi o.oos oa
Grain Size in Millimeters
GRAVEL SAND
Coaru
Tint Coarse Medium
Fine
SILT of CLAY
0
10
20
30
40
50
60
70
80
90
100
31
Figure 3. Typical grain-size distribution curves for soils
-------
TABLE 1. UNIFIED SOIL CLASSIFICATION SYSTEM
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INCREASING MOISTURE CONTENT
SOLID
SEMISOLID
PLASTIC
SEMILIQUIO
LIMIT
LIMIT
LIMIT
Figure 4. Relationship of Atterberg limits
to water content
20
-------
expressions for the consistency of clays in terms of qu are given in Table 2.
If equipment for making unconfined compression tests is not available, a
rough estimate can be made based on the simple field identification suggested
in the table; various small handheld penetration or vane devices are also
helpful.
Compaction tests: Compaction tests are performed on cohesive soils and on
dirty coarse grained soils. At a constant compactive effort, an impact or
kneading compaction is applied at various water contents. The result is a
density/water content relationship, such as shown in Figure 5, in which-the
maximum density and the optimum water content are defined. Test results vary
with changes in soil type, type of compaction, and compactive effort.
Relative density tests: For clean, coarse grained soils the maximum
achievable density (by vibration) and minimum achievable density (by pouring)
are compared to an in situ soil density. The in situ value is then calculated
relative to the laboratory defined maximum and minimum values for the same
soil. It is possible to have field densities greater than the maximum or less
than the minimum since these values are defined by the results of certain
standardized tests. An example is given in Figure 6.
Compaction tests and/or relative density tests are generally used to
establish limits or goals for field compactive effort. The attainment of a
specified degree of compaction is expected to provide a compacted fill soil
having the desired engineering design properties, i.e. permeability, compressi-
bility, and shear strength.
Additional Tests
There is, in addition to the laboratory index properties tests described
above, a small group of useful tests which, because of their simplicity, almost
classify as observations. They include the field expedient tests of Table 1.
Field expedient tests ; These soil identification tests are based on vi-
sual examination and simple manual tests; they do not yield a numerical result.
They are described in detail in ASTM (1982) Designation D 2488-69, "Standard
Recommended Practice for Description of Soils (Visual-Manual Procedure)".
Color; The color of a soil sample, particularly in its natural moisture
condition, is a useful method for correlating similar soils and for identify-
ing water table conditions. A formal method using Munsell color charts is
available for classification by colors (Spangler and Handy, 1982).
Organic content: ASTM (1982) Designation D 2488-69 and various geo-
technical textbooks describe expedient methods for identifying organic soils.
These methods include observation of the soil's dark color or earthy odor.
Heating or hydrogen peroxide solution will destroy the organic matter,
permitting classification. Formal chemical analysis methods are referenced in
Section 4.
21
-------
TABLE 2. DETERMINATION OF THE CONSISTENCY OF CLAYS
Unconfined
Compressive
Strength, q
tsf
u
Less than 0.25
0.25 - 0.5
0.5 - 1.0
1.0 - 2.0
2.0 - 4.0
Over 4.0
Field Identification
Easily penetrated several inches by fist
Easily penetrated several inches by thumb
Can be penetrated several inches by thumb
with moderate effort
Readily indented by thumb but penetrated
only with great effort
Readily indented by thumbnail
Indented with difficulty by thumbnail
Consistency
Very soft
Soft
Medium
Stiff
Very stiff
Hard
22
-------
120
115
I i I
NOTE: DETERMINATION OF OPTIMUM
WATER CONTENT AND MAXIMUM
DRY DENSITY SHOWN FOR LEAN
CLAY ONLY.
SAMPLES COMPACTED USING CE 55
COMPACTION EFFORT. CLASSIFI- —
CATION DATA FOR SAMPLES SHOWN
IN FIGURE 2-3
MAXIMUM DRY DENSITY
= 107 LB/CU FT
OPTIMUM WATER
CONTENT = 18.0%
LEAN CLAY
(CL)
UNIFORM FINE
SAND
(SP)
MAX DRY DENSITY
COMPACTION
CURVE
FAT CLAY
(CH)
WATER CONTENT
75
Figure 5.
10 IS 20 25
WATER CONTENT, PERCENT DRY WEIGHT
Typical density-water content relationships
for compacted soils
23
-------
150
140
Z 130
i
u.
u
0.
DENSITY,
O
g 100
90
1
TO USE:
^^
I 1
PLOT rwiN =99.0, -XMAX =119
SHOWN AND CONNECT WITH S
LINE rd = HO. PCF FOR Dr
Td = 114.4 PCF
^^
•**^
FOR Or = 80%,
^— -EX/
PCF, AS
TRAIGHT .
= 60%
ETC.
-**--
^^^
MPLS
l^^
~*^^
ISO
X
130 *
-e
I
H
U
0
' DENSITY
K
500 Q
9O
20 40 60 60
RELATIVE DENSITY, Dr PERCENT
100
D s percent = —
r IY
v — v
Yd Ydmin
dmax
dmin >
\
where
D = relative density, in percent
Y, = dry unit weight of the soil in places called "in-place" density
Y, . = dry unit weight of the soil in the loosest state which can be
dmin
attained in a particular laboratory test called "minimum
density"
Y, = dry unit weight of the soil in the densest state which can be
max attained in a particular laboratory test called "maximum
density"
Figure 6. Example of graphical solution of relative
density relationship
24
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THE POST-PERMIT STAGE
This section of the report presents those geotechnical observations
and/or tests that should be made and documented during the construction,
operation, and closure of a disposal site. The presentation is made in the
-context of the various unit processes involved. The observations/tests and
documentation will be the same for the same unit process, regardless of its
location on the project.
Only those unit processes, or portions of processes, whose quality .of
materials and workmanship directly affect the ability of the site to meet
specified performance standards are presented. The emphasis in the discussion
presented for each process is on a quality assurance program that focuses on
catching mistakes before or as they occur, correcting them, testing for
specification compliance, and documenting the entire process to provide the
necessary confidence in the inspection procedure. During the conduct of each
unit process, there must be continuous, cooperative interaction between the
groups within the permittee's forces responsible for the design function, the
inspection function, and the construction and operations function to secure the
required verification of design assumptions and quality of work, along with
the effective, efficient, and profitable use of men, machinery, and materials.
Inspection Reports
Documentation of the necessary site geotechnical verification work, the
required inspection observations and tests, and their interpretation, should
be part of the total project record. As will be presented in greater detail
in Section 5 of this report, the project records will include daily inspection
reports, field/laboratory data sheets, block* evaluation reports, design
acceptance reports, and a summary.
Site Preparation
The process of site preparation includes clearing, grubbing, stripping,
and grading (U.S. Bureau of Reclamation, 1974; Church, 1981; and Dept. of the
Army, 1977). The primary purposes for this activity are (a) preparation of
each specific disposal facility for excavation and/or embankment placement,
(b) construction of haul roads, and (c) altering the site drainage patterns.
The following observations/tests should be made and documented:
a. Observations of the exposed ground surface in the site limits,
following stripping, as part of site media confirmation. Normally,
only the visual-manual field identification procedures shown in
Table 1, Unified Soil Classification System or ASTM (1982)
The term block is used in this report in preference to the more commonly
used term, lot, from the field of Statistical Quality Control. It is the
authors' opinion that the word lot implies a number of discrete units from
a continuous manufacturing process. The term block is more appropriate to
bulk materials such as a soil mass.
25
-------
Designation D 2488-69, will be necessary. If an unexpected material
or zone configuration is encountered, then more formal tests may be
necessary.
b. Observation of ground surface contouring measurements to confirm
adherence to the planned drainage pattern, preferably these should
be surveyed measurements
c. Observation of the performance of the surface drainage system, during
the first significant rainfall, to identify erosion or ponding
problems
Excavation
The preparation of a disposal facility may involve (a) the excavation
of one or more trenches below the ground surface, and/or (b) the stripping and
shaping of a natural or man-made depression. The latter may be a gully,
small canyon, or similar erosional feature, wholly or partially enclosed by
an earthfill embankment, or it may be a former strip mine, borrow pit, or
similar feature. All are characterized by having the floor and at least one
wall consisting of the stripped and shaped, naturally occurring site soils.
The observations and tests that should be made and documented regarding
the excavated walls and floors of a disposal facility include:
a. Detailed observations and descriptions should be made of the exposed
walls and floor for the purpose of site media confirmation. These
should be supplemented by confirmation tests for those features that
conform to the site characterization studies. Photographs are often
of value. The tests will usually consist of field consistency tests
and those tests required for the USCS classification, i.e., grain-size
distribution and/or Atterberg limits. More extensive testing may be
necessary if an unanticipated material or zone configuration is
encountered. Undisturbed samples and engineering properties tests may
be justified, with additional samples tested for index properties.
Observed differences from expected site characterization should not
only be recorded, but should also be immediately reported to the
permittee's group responsible for the design function for their
consideration of possible remedial action.
b. Observations should be recorded of the construction surveys involving
trench location, slopes of walls, and slopes of floors. Conformance
with planned slopes should be noted.
c. During and after construction, visual observations, supplemented by
surveying where necessary, should be made and recorded of excavation
related soil movements. These should include heaving and/or cracking
of the floor, and of slaking, sluffing, creep, sliding, or other move-
ments of the side walls. Again, photographs may be of great documen-
tary value. Survey monuments, placed at the start of construction,
should provide documentable data.
26
-------
d. Observations should be recorded of erosion controls for conformance
with plans. These may include trench-top perimeter ditches and/or
dikes and the placement of any spray-on erosion-inhibiting material,
including the material's identification.and application rate.
Foundation Preparation
If an earthfill embankment is used to partially or completely enclose a
disposal facility, the natural foundation and abutments must, as discussed in
Engineer Manual 1110-2-1911 (Dept. of Army, 1977), (a) provide positive control
of underseepage, (b) provide satisfactory contact with overlying compacted
fill, and (c) minimize differential settlements and thereby prevent cracking
in the fill. The observations and tests made and recorded during foundation
preparation should include:
a. Observations should be recorded of the stripping to assure that all
soft, organic, or otherwise undesirable materials are removed.
Consistency (Table 2) may be checked by a hand penetrometer or similar
device. Proof-rolling by construction equipment is often used to
locate soft areas. Organic soils may be identified by the procedures
given in Table 1.
b. Observations should be recorded of the soil and rock surfaces for
smoothness, adequate cleaning, filling of rock joints and of
depressions.
c. Observations should be recorded of the construction of underseepage
cutoffs, if used, to check required depth, materials encountered,
backfill materials used, and proper placement of backfill. If
compacted fill is used, then it should be observed/tested as for
other fills as discussed below.
Compacted Earthfill
Compacted earthfill embankments may be used to partially or completely
enclose a disposal facility. Where a liner is used, it may include a compacted
soil hydraulic barrier and a compacted granular hydraulic conductor layer.
The final cover may also include a hydraulic barrier and a hydraulic conductor
layer, overlain by a vegetation supporting layer.
The waste contained by the embankment and/or liner system may, in a
disposal facility, consist of solid wastes with moist soil backfill which may
eventually become saturated with water, or in the case of a surface impound-
ment, it may consist of a high water content slurry. If appreciable steady-
state seepage is expected through the embankment, then internal seepage con-
trol features such as filter drains and underseepage control measures may be
needed. The liner system may contain a hydraulic barrier, such as a
geomembrane, supported by a compacted, low permeability cohesive soil. It
may also contain a hydraulic conductor, usually a granular filter material
of high permeability, connected to a leachate collector system.
The observations and tests that should be made (Dept. of the Army, 1977;
27
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and USER, 1973) and recorded during compacted fill placement, using cohesive
or granular soils, are presented below (A similar discussion of off-site
materials placed on, or incorporated into, the compacted soil part of the
liner system is given later in this report.):
a. The quality of the borrow materials must be tested. The source of
the borrow may be a natural borrow pit or a stockpile of soil from
a trench excavation. Two or more soils may be blended to produce a
desired gradation or plasticity. Samples of the borrow materials
should be tested for USCS classification (grain-size distribution
and/or Atterberg limits) and for natural water content. If admixes
are blended into the natural soil, the application rate and uniformity
of mixing should be observed and documented.
b. Atmospheric conditions should be recorded. Compaction specifications
often place restrictions on work performed just after a rainfall
during very hot or windy weather, or during freezing conditions.
c. Equipment type, size and compatibility with the soil type must be
evaluated and recorded. For cohesive soil, a sheepsfoot roller, a
tamping roller, or a rubber tired roller may be used. For clean,
granular soil, a. vibratory roller is appropriate. As given in
Engineer Manual 1110-2-1911 (Dept. of the Army, 1977), items to be
checked and recorded include: (a) for a sheepsfoot roller, drum
diameter and length, empty weight and ballasted weight, arrangement
of feet and length and face area of feet, and the yoking arrange-
ment; (b) for a rubber tired roller, the tire inflation pressure,
spacing of tires, and the empty and ballasted wheel loads; and
(c) for a vibratory roller, the static weight, imparted dynamic
force, operating frequency of vibration, and the drum diameter
and length.
d. The uncompacted or loose lift thickness should be systematically
measured at several statistically valid locations in a layer of fill.
Both actual thickness and uniformity of lift placement are of impor-
tance. Loose lift thicknesses of (a) 6 to 8 in. for a sheepsfoot
roller, or (b) 9 to 12 in. for a 50 ton rubber tired roller are
usual for cohesive soils; while clean, granular soils should have
loose lifts of (c) 6 to 15 in. when using a vibratory roller or
50 ton rubber tired roller, or (d) 6 to 8 in. when using a crawler
tractor (Dept. of the Army, 1977). Measurements are usually made
with a marked staff or shovel blade, although survey levels should
be made every few lifts for verification and documentation.
e. Compactive effort and uniformity of compaction should be observed and
recorded. Compactive ef.fort can be changed by changing the number of
passes of the roller, by changing the size and weight of the roller,
and/or by changing lift thickness. For cohesive soils (a) six to
eight passes of a sheepsfoot roller or (b) four coverages of a 50 ton
rubber tired roller are usual; while for a clean, granular soil
(c) three or four passes of a vibratory roller or (d) three to six
coverages of a crawler tractor are usual (Dept. of the Army, 1977).
28
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Uniformity of coverage should be closely observed, particularly at
fill edges and in turn around areas. When a crawler tractor is used,
the coverages must be by the tracks of the tractor.
f. Compacted density and water content should be measured and recorded.
The coordinate location of each test and the elevation of the ground
surface should also be measured. The latter is a check on lift
thickness; and when a retest of unacceptable fill is necessary,
serves to verify that no additional fill has been placed.
g. Laboratory compaction tests should be made of samples of the same
fill soil whose field density and water content were measured in
item (f.) above. The effectiveness of the compactive effort in the
field is referenced to the laboratory compaction test. Specifica-
tions for cohesive soil and dirty granular soil compaction require
achievement of a minimum percentage of the maximum density, at a
water content within a specified range and related to the optimum
water content, as determined by the specified laboratory compaction
test procedure. Figure 5 shows typical impact-compaction laboratory
test results. For clean granular soils, which densify more readily
under vibration than under impact, a minimum relative density or a
minimum percentage- of the laboratory maximum dry density is usually
specified. This involves comparison of the density of the field
compacted' soil with the maximum and minimum densities for the same
soil developed in a specified laboratory procedure. Figure 6 shows a
graphical comparison procedure using an ordinate for dry density
scaled for solution of the relative density equation.
Liner Materials and Geotextiles
The construction of a hazardous waste disposal facility may include the
construction"processes involved in liner material or geotextile installation.
The hydraulic barrier layer of the liner is expected to provide a permeability
lower than a required value. When this criterion is not present in the natural
cut soil of the floor and walls or cannot be effectively achieved in a com-
pacted soil fill layer, then off-site materials may be used. These may consist
of bentonitic clay, Portland cement, asphalt, lime, or similar materials that
are admixed throughout, or are mixed with only the surface lift of the com-
pacted soil of the barrier. The barrier may also be a spray-on material or a
geomembrane. Geotextiles may also be used as a filter aid or for soil
reinforcement, e.g. slope stability or trench cap strength.
The tests and observations that should be made and recorded during liner
material or geotextile installation are generally material dependent:
a. For all off-site materials used (liner materials and geotextiles)
the type and supplier's identification for the material should be
recorded. Lot numbers or their equivalent are used to trace mate-
rials of substandard quality to specific manufacturing procedures.
b. For bentonitic clay and admixed material liners the tests and observa-
tions are those that would be conducted to determine the field
29
-------
permeability of any soil layer, i.e. to include density testing and
observation of layer thickness. (These tests and observations are
discussed in the previous subsection on Compacted Earthfill.)
c. The tests and observations for the installation of a Portland
cement or asphalt liner are deemed to be beyond the scope of this
report as they are not within the framework of soils engineering
per se. References describing these tests and observations are
readily available from the Portland Cement Association and the
Asphalt Institute.
d. For admixed materials, the spreading and mixing, or blending equip-
ment and procedures should be observed and recorded. Reference
should be made to industry standard methods, to manufacturer's
recommended procedures, or other descriptions of the state of the
art for the methods.
e. For admixed materials, the application rate should be observed and
recorded. The methods used for verifying the application rate, such
as the calibration of spreading devices, should also be recorded.
f. For admixed materials, compaction of the soil-admixture blend should
be observed, tested, and recorded in the same manner as described
earlier for Compacted Earthfill. Soil classification tests, observa-
tions of lift thickness and of uniformity of rolling, observations
of the suitability of blending and compacting equipment, and the
comparison of field density (and water content, if applicable) with
the specified laboratory control test, should all be made and
recorded.
g. For spray-on materials, the observations and tests include identifi-
cation of the material, verification of manufacturer's quality tests,
application equipment suitability, application technique comparison
with state-of-the-art directions, application rate, application
thickness, and uniformity of coverage.
h. For geomembranes or geotextiles, the supplier's materials identifi-
cation marks should be compared with the purchase order or catalog
descriptions. The smoothness of the placement surface, and its
freedom from objects that might puncture the material, should be
verified. If required, test specimens may be cut from the field
sheets; this will require patching and the patching itself should
also be observed and recorded. The method of placement of the
material should be recorded and supplemented by photographs if possi-
ble. The seams should be inspected at frequent locations and the
required seam overlap measured and recorded. The method of sealing
the seam, whether thermal or adhesive, should be observed and
recorded; all seam formation should be closely inspected. Seam
integrity tests, if specified, should be made and the results
recorded, including notation of the locations of the tests. The
entire placed material should be systematically inspected for imper-
fections or tears and the results of the inspection recorded. When
30
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appropriate, as determined by the permittee's forces (e.g. for a
surface impoundment), a hydrostatic leak detection test may be per-
formed. If a hydrostatic leak detection test is performed then the
entire submerged geomembrane should be systematically inspected for
leaks.
Hydraulic Collector System
The disposal facility bottom liner and the final cover may both contain a
permeable layer above the hydraulic barrier. Its function is to change .the
direction of the percolating water from a downward movement to a horizontal
movement toward a nearby collector drain. Usually it is formed of a clean
granular material placed directly on the surface of the impermeable hydraulic
barrier. The surface of the barrier is sloped toward the collector system,
usually located at the perimeter of the disposal unit. Observations and
tests that should be made and recorded for this feature are:
a. The surface of the base for the permeable layer should be inspected
and observations recorded. Imperfections include soft soils,
organic materials, the lack of specified admix or spray-on material,
or leaks in a geomembrane.
b. The amount and direction of slope of the permeable layer base should
be verified and recorded. This will usually involve standard survey-
ing techniques.
c. The clean granular materials used in the permeable layer should be
tested for grain-size distribution, particularly for the presence
of undesirable fines. Comparison should be made to the specified
grain-size requirements.
d. The "placement, compaction, field density testing, and relative den-
sity testing should be performed and recorded as described above for
Compacted Earthfill.
31
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SECTION 3
SAMPLING METHODS AND SELECTION OF SAMPLE SIZE
There is an inherent, or natural, random variability in measurement data
for any specified quality characteristic of any soil mass, or other construc-
tion material, whether natural or construction processed (Terzaghi and Peck,
1967). This is due to natural, point-to-point, variations in material quality
and random variations due to the sampling and testing procedures. It is
assumed in this discussion that this natural variability has been considered,
either formally or intuitively, in the establishment of (a) the design assump-
tions regarding the engineering properties of the existing site media and
(b) the specifications for materials and workmanship in the construction
processes.
Inspection of the existing site media exposed during construction, and
of the material and workmanship of the construction processes, is an essential
part of the construction quality assurance program. Where a 100 percent
inspection is not practical or is clearly uneconomical, one or more samples
are obtained and tested. The resulting sample data are used to estimate a
quality characteristic of the soil mass they represent. The usefulness of
samples in representing the soil mass is a function of the manner of sampling,
i.e. the size of the soil mass (block), the manner of selecting sampling
locations and times, the number of samples or measurements per block, and
the sampling and testing procedure. These, in turn, affect the method of
evaluation of the sample with regard to specified or assumed quality
characteristics.
The establishment of sampling methods and of sampling and testing fre-
quency may be based on either (a) judgement or experience, or (b) proba-
bilistic methods using statistical theory (Deming, 1950). Up until the last
10 to 15 years, Willenbrock (1976) states, "...quality of construction was
largely accomplished through semi-artisan techniques and procedures with
constant visual inspection." Judgement methods were, and still are, subject
to biases and sampling errors (Deming, 1950) dependent on the knowledge,
capability, and experience of the specification writers, the inspector,
and/or his supervisor. These factors cannot easily be evaluated or docu-
mented. Therefore the more rational, calculable, and documentable methods
using statistical theory are recommended. The human factor (see Section 5),
with its prejudice and bias, can thus largely be eliminated. If sampling,
whether judgemental or random, is to be used to evaluate and/or control
compaction or any other construction process, then it is imperative that a
well defined procedure be used consistently. If the procedure is altered,
then a change in population characteristics occurs, and the sample becomes
biased.
32
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As background for the presentation of sampling and testing frequency,
the natural variability of measured engineering soil properties is discussed.
Several sources of variability data from the engineering literature are
presented as preliminary sources for obtaining data. The sources of
variability in soils, as measured by the various index properties tests,
is presented. .This is followed by a discussion of accuracy and precision
of measurements. The effect of test method precision is developed as it
relates to selection among alternative test methods. Types of inspection
and sampling plans are presented. Forms of random sampling plans are
recommended and illustrated by an example. The rational selection and/or
evaluation of sample size, based on quality variance, maximum expected error,
and confidence level, is presented in statistical terms. Finally, the
statistical methodology and interpretation of calibration and sample size
are given.
Although this section of the report discusses sampling and testing
using statistical analysis terms, equations, and tables, it is not intended
to be a complete treatise on the subject. Its aim is to introduce the topic
and describe its application to quality assurance in hazardous waste disposal
facility construction. The interested reader should consult more complete
discussions of the various topics in standard textbooks on engineering
statistics and professional journal articles.
VARIABILITY OF MEASURED PROPERTIES
Soils are generally used in their natural state, unaltered by the homog-
enizing manufacturing processes of, for example, structural metals, portland
cement, or asphalt cement. The measured properties of interest in this dis-
cussion are those given in Section 2: the engineering soil properties; the
soil index properties; the specified quality characteristics of off-site
materials; and many of the observations of construction processes. This dis-
cussion can'easily be extended to include geochemical and geohydrologic
properties.
The variability in the properties of natural soils, whether undisturbed
or processed, has been recognized for some time by geologists, soil scien-
tists, and geotechnical engineers (Terzaghi and Peck, 1967). The literature
of these disciplines, particularly since the middle 1950rs, contains many
studies of soil property variability. The literature is so voluminous
that it would be burdensome for this report to reference all of it. There-
fore, only a few, representative reference sources will be given.
Natural Soil Deposits
The variability of the properties of natural soil deposits is discussed
in general terms in most textbooks on geotechnical engineering and engineering
geology. Very good descriptions are given, for example, in Peck, et al.
(1974), Harr (1977), Sowers (1979), and Spangler and Handy (1982). Studies
of the variation of soil index properties in soil survey mapping units were
given in Thornburn, et al. (1970) and Campbell (1978). An interesting study
of field infiltration rate variation over a limited site was given by
33
-------
Vieira, et al. (1981); this information may be of value in planning testing
programs for verifying the permeability of existing site media, compacted
clay liners and covers. Harr (1977) has compiled data from a number of
literature sources. Table 3 is a summary of Harr's tabulations.
Compacted Soils.
The published data for compacted soils comes mainly from two sources:
(1) earth dams and (2) highway embankments construction. Davis (1953) first
reported statistical evaluation of control tests for Bureau of Reclamation •
dams. Several Corps of Engineers projects were evaluated for water content
and density variation by Turnbull, Compton, and Ahlvin (1966). They showed
moisture content had a standard deviation from 1.2 to 1.9 percent and that
density had a standard deviation from 1.88 to 2.32 Ib/cu ft. Davis (1966)
summarized earthwork control statistics from 72 Bureau of Reclamation earth
dams. He concluded that fill moisture content had a standard deviation of
less than about 1.5 percent and density had a standard deviation of less than
about 3.0 percent. A summary tabulation of Davis' data is contained in
Table 7.10 of the textbook by Winterkorn and Fang (1975). Reporting on a
Corps of Engineers project (DeGray Dam, Caddo River, Arkansas), Strohm and
Torrey (1982) presented compaction control data in general agreement with
Turnbull, Compton, and Ahlvin, and with Davis. For the cohesive soils of the
core and shells of the dam, and based on several hundred tests, fill water
content had a standard deviation of 1.24 to 1.63 percent, while the fill
compaction had a standard deviation of 2.61 to 2.87 percent. Figures 7, 8,
and 9 are from the Strohm and Torrey report. They show the variation in
control test data for the clay core of the dam.
Starting in the late 1950's, at the urging of the U. S. Bureau of Public
Roads, there were numerous studies and reports of natural variability of
compaction data on highway projects. Typical of these are Miller-Warden
(1965), Redus and Spigolon (1965), Jorgenson (1969), and Essigman (1976).
The reported variations for fill density had standard deviations as high as
5.5 percent with a coefficient of variation up to 5.9 percent. For water
content, standard deviation values were as high as 3.6 percent with a coeffi-
cient of variation of 24 percent. The higher values, compared with the Corps
of Engineers and Bureau of Reclamation data, probably represent (a) less
stringent quality control measures, or (b) greater variability in borrow
materials along the lengths of the highways, or (c) both.
SOURCES OF VARIABILITY
The frequency histograms of Figures 8 and 9 are illustrative of the
natural variability of test data from a construction process. Similar repre-
sentations can be made for measurement data for any other quality characteris-
tic from natural or processed soil masses. Thus the need for statistical
analysis as part of the geotechnical quality assurance of the construction of
a hazardous waste disposal facility is clear.
A universe, or population, is defined as the totality of the set of
measurements of the quality characteristic under consideration. Its
34
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TABLE 3. VARIABILITY OF NATURAL SOIL DEPOSITS*
Parameter
Void Ratio
Porosity
Specific Gravity of
Solids
Water Content
-
Unit Weight
Degree of Saturation
Unconfined Compression
Strength, tsf
Material
Gr. Sand
Cs . Sand
Med. Sand
Fine -Sand
Silt
Silty Clay
Clay, 5 ft
10 ft
15 ft
20 ft
Gr. Sand
Cs . Sand
Med . Sand
Fine Sand
Silt
Silt
Silty Clay
Clay, High PI.
Clay, Med. PI.
Clay, Low PI.
Silt
Silty Clay
Clay, 4 ft
10 ft
16 ft
20 ft
Clay, 20 ft
Clay, High PI.
Clay, Med. PI.
Clay, Low PI.
Clay, High PI.
Clay, Med. PI.
Clay, Low PI.
Silt
Clay, 5 ft
10 ft
15 ft
20 ft
Clay, 5 ft
10 ft
15 ft
20 ft
Clay
Clay
Clay Shale
Clay Till
Clay Till
No. of
Samples
93
67
38
70
327
57
120
96
47
' 21
93
67
38
70
327
329
4
65
65
65
406
790
430
415
307
177
29
98
99
97
97
99
97
334
111
90
38
18
279
295
187
53
231
97
— ,
-.-
•_<_
Mean
0..506
0.570
0.686
0.663
0.631
2.33
0.900
0.911
0.909
0.749
0.330
0.399
0.404
0.390
0.383
2.563
2.66
2.63
2.66
2.69
0.206
0.84
0.289
0.328
0.355
0.348
0.217
0.206
0.131
0.138
113.3
115.8
112.5
0.845
0.919
0.956
0.975
0.933
2.08
1.68
1.49
1.30
0.97
—
—
3.24
Standard
Deviation
0.150
0.107
0.128
o.'oss
0.136
•0.46
0.157
0.138
0.186
0.236
0.062
0.039
0.041
0.032
0.051
0.029
0.05
0.115
0.060
0.054
0.047
0.19
0.051
0.039
0.043
0.046
0.028
0.027
0.0082
0.0092
2.8
14.2
2.09
0.162
0.121
0.086
0.084
0.080
1.02
0.69
0.59
0.62
0.26
—
—
—
1.17
Coeff. of
Variation
29.6
18.8
17.5 -
13.3
21.6
20.0
17.5
15.1
20.4
31.6
18.6
9.8
10.1
8.0
13.3
1.1
"1.87
'4.4
2.3
2.0
22.8
22.0
17.7
11.9
12.2
13.2
12.9
13.1
6.3
6.7
2.5
12.3
1.9
19.2
13.2
9.0
8.6
8.5
49.1
40.9
39.6
47.7
29.0
30-40
37-51
60-85
36.1
Adapted from Tables 10-1 and 10-3 of Harr (1977).
published sources.
Data are from several
35
-------
160
150 hr
140
130
120
cc
Q
- 110
100
90
80
V
j
i i i
MEAN RESULTS
NOTE: ALL DATA PERTAIN TO THE MINUS 1 IN. FRACTIONS
OF THE FILL DENSITY SAMPLES.
I
I
I
I
I
I
1
12 16 20 24 28
FILL WATER CONTENT, PERCENT
32
36
Figure 7. Results of compacted fill tests, DeGray Dam, Caddo River,
Arkansas (Strohm and Torrey, 1982) .
36
-------
j SPECIFIED RANGE OF WATER CONTENT]
50
40
< 30
w
20
o
a.
10
1 I I 1 I I I l
N = 154
a = 1.24 PERCENTAGE POINTS
X = 0.25 PERCENTAGE POINTS
DRY OF OPTIMUM
SPECIFIED
LIMITS
I I
MEAN
NORMAL CURVE -
JALM
~H
i i
100
80
z
I 60
H
(/)
a>
-2
40
-8-7-6-5-4-3-2-1 01 234567
VARIATION OF FILL WATER CONTENT FROM LABORATORY
OPTIMUM PERCENTAGE POINTS
PERCENT OF TOTAL SAMPLES WITH
RESPECT TO ONE STD. DEV. (a)
BELOW
9.74
WITHIN
81.17
ABOVE
0.00
20
I !
I I
-8 -7 -6-5-4-3-2-1 0 1 2 3 4 5
VARIATION OF FILL WATER CONTENT FROM
LABORATORY OPTIMUM PERCENTAGE POINTS
PERCENT OF TOTAL SAMPLES WITH
RESPECT TO SPECIFIED LIMITS
BELOW
4.55
WITHIN
88.31
NOTE- ALL DATA PERTAIN TO THE MINUS 1-IN. FRACTIONS OF THE
FILL DENSITY SAMPLES.
N = NUMBER OF TESTS
O = ONE STANDARD DEVIATION EXPRESSED IN PERCENTAGE
POINTS RELATIVE TO THE MEAN VARIATION OF FILL
WATER CONTENT FROM LABORATORY OPTIMUM
X -- MEAN VARIATION OF FILL WATER CONTENT FROM
LABORATORY OPTIMUM EXPRESSED IN PERCENTAGE
POINTS
VARIATION OF FILL WATER
CONTENT, CORE OF THE DAM
Figure 8. Fill water content variability, DeGray Dam, Caddo River,
Arkansas (Strohm and Torrey, 1982).
-------
50
40
< 30
CO
o
o:
OJ
oo
20
10
I I I I I I I I"
N= 154
0 = 261 PERCENTAGE POINTS
- X = 103.36 PERCENT COMPACTION
DESIRED
MINIMUM
MEAN
III!
NORMAL CURVE
100
80
6°
DESIRED MIN. PERCENT OF MAX. STD. DRY DEN.
100
40
20
I I i
i r
i i i i i i i
85 89 93 97 101 105 109
FILL PERCENT COMPACTION
PERCENT OF TOTAL SAMPLES WITH
RESPECT TO ONE STD. DEV. (a)
113
117
BELOW
1523
ABOVE
11.69
84 88 92 96 100 104 108
FILL PERCENT COMPACTION
PERCENT OF TOTAL SAMPLES WITH
RESPECT TO DESIRED % COMPACTION
112
116
BELOW
10.59
ABOVE
89.61
NOTE: ALL DATA PERTAIN TO THE MINUS 1-IN. FRACTIONS OF THE
FILL DENSITY SAMPLES
N = NUMBER OF TESTS
a- ONE STANDARD DEVIATION EXPRESSED IN PERCENTAGE
POINTS RELATIVE TO THE MEAN VARIATION OF FILL
WATER CONTENT FROM LABORATORY OPTIMUM
X = MEAN VARIATION OF FILL WATER CONTENT FROM
LABORATORY OPTIMUM EXPRESSED IN PERCENTAGE
POINTS
VARIATION OF PERCENT
COMPACTION, CORE OF
THE DAM
Figure 9. Fill density variability, DeGray Dam, Caddo River,
Arkansas (Strohm and Torreys 1982).,
-------
frequency distribution, usually based on a hypothetically infinite number of
measurements, will typically have a form similar to that shown in Figures 8
and 9. The distribution can be characterized by a central value, the mean,
and by the dispersion about that value, the standard deviation (or its
square, the variance).
The numerical difference between the measured value of a characteristic
and its mean, true, or reference value is termed its error. That term is used
here in the statistical sense as defined and does not include error from a
faulty measurement or mistake in calculation, unless the fault or mistake is-
included in all measurements consistently.
Variations, or errors, can be (a) random or (b) nonrandom, or
(c) both. Random errors occur without aim or reason, depending only on
chance. This uncontrollable variation results in measured values that are
clustered about the central, mean value (Figures 8 and 9) and whose magnitude
is characterized by the variance (or standard deviation) of the data.
Nonrandom errors are due to some significant, assignable cause, or causes.
The error cause may change abruptly, such as change from one soil type to
another, or gradually, such as the spatial variation that often occurs
horizontally in a soil layer. When variation occurs due to an assignable
cause in a construction process, and the cause is recognized, the effect can
be accounted for and often controlled.
Variation in measured characteristics of a soil mass universe stem from
three causes. Williamson and Yoder (1967), Essigman (1976), and Price
(1978) have described these error causes as:
a. Material composition variability
b. Placement process variability
c. Measurement process variability
Material Composition Variability
Soils are the product of degradation of rock. As stated by Peck, et al.
(1974), "In a very general way, soils tend to be arranged in profiles or
systems of layers. The most significant of these are profiles of weathering
and profiles of deposition." Significant changes in engineering properties
occur as a result of changes in soil type. Within a sample unit from a
homogeneous soil mass, random variations occur because of the heterogeneity
of the mineral composition of the parent rock, and because of the nonuni-
formity of the degradation process. Grain sizes, grain shapes, clay content,
mineralogy, and nature of the pore fluid in the soil are composition
variables.
Placement Process Variability
The process of placement of the soil, whether in its natural state or
in a compacted fill, will result in variability in measured characteristics.
Natural depositional processes tend to be uniform within a small area, such
39
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as a sample unit, or even a batch, or an entire block. However, spatial
variation, vertically or horizontally, can occur gradually or abruptly as
discussed above. The variations occur because of changes in the geologic
processes of transportation, deposition, compaction under overburden, and
erosion. In a soil of constant composition, processing affects void ratio,
degree of saturation, the flocculated or dispersed structure of the clay
fraction, and the shape and arrangement of pore spaces.
In earthfill operations, causes of nonrandom variations have been listed
by Turnbull et al. (1966). In addition to changes in soil composition in
the borrow areas, they are caused "... by changes in borrow operations,
including water content adjustment, mixing and loading; by changes in opera-
tions on the fill, including number and type of hauling, spreading, and
compacting equipment, water content adjustment, and placement methods; ands
finally, by Nature in the form of periods of freezing temperatures, rains,
and aridity in the construction area." Random variations may occur due to
nonuniform coverage of the feet of a sheepsfoot roller or of the wheel
prints of a rubber tired roller; or due to randomness in point-to-point lift
thickness, roller speed, temperature, and water content (Essigman, 1976;
Price, 1978).
Measurement Process Variability
The specific technique for a test will involve several factors. Changes
in significant details of procedure, in the test technician, in technician
fatigue, in instrumentation of the same kind or of different types, and in
the ambient environmental conditions may cause a systematic, or bias, effect
on test results. The measurement process may even be considered to include
the sampling process. And therefore changes in sampling can result in non-
random variation. Even if all other conditions are held constant, repeated
tests on the same test portion by the same technician using the same equipment
and procedure will result in random test values. These are caused by the un-
assignable and uncontrollable accumulation of small variations that are part
of any testing process.
ACCURACY AND PRECISION OF MEASUREMENT
Considering the causes of variation in measurements as presented above,
the topic of accuracy and precision of test methods can be discussed. In
this discussion, the notations of Hald (1952) and of ASTM (1982) Designation
E 177-71, "Use of the Terms Precision and Accuracy as Applied to Measurement
of a Property of a Material", have been combined.
The measurements that constitute a sample can be combined into a group
of sample statistics:
a. The arithmetic average, or mean- is defined as
I - (3-1)
40
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b. The variance is
a2 = - (3-2a)
n
c. The variance may be written in an alternate form, to be used when
the sample size is small (say less than n = 30), as
- X)2 ,
n - 1
d. The standard deviation is the square root of the variance.
e. The coefficient of variation expresses the standard deviation
as a percentage of the mean
(3-4)
X
where X = numerical value of a measurement
n = number of individual measurements in the sample
V = coefficient of variation
E = mathematical symbol for summation from one to n
e = deviation of individual measurement from the mean
Each individual measurement of a quality characteristic may be con-
sidered to be one of a hypothetically infinite number of similar measurements
that could be made in a universe of the material. The difference or error
between the measured value and the true or reference value is the sum of two
components, an accuracy (systematic or calibration) error and a precision
(random) error. This can be written as:
and
X = UR + 6 + £ (3-5)
5 = UR - Pp (3-6)
41
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where X = numerical value of a measurement
u = true or accepted reference level of the property of the material
to be measured
y = expected value or the average of many observations recorded for
the process
6 = correction for consistent or systematic error of the measurement
process at the reference level y
K
e = correction for random deviation about the average of the
observation y
Accuracy refers to the degree of agreement of individual measurements
or the average of a large number of measurements with a true or accepted
reference value. This implies the idea of a consistent deviation, or
systematic or bias error, which is a fixed or common contribution to error
in each of a sample of measurements. Precision is the degree of mutual
agreement among individual measurements of a consistent material made under
prescribed, like conditions. The imprecision of measurement may be character-
ized by the standard deviation of the errors of measurement.
Accuracy Error
In Equation 3-5, the 6-term for correction for systematic, or accuracy,
error is the sum of corrections from each of the three causes of nonrandom
variation. This is then written:
6 - S + 6 + S (3-7)
where 6 = correction for systematic error due to material composition
6 = correction for systematic error due to placement process
S_ = correction for systematic error due to testing process
Because the effects of material composition, placement process, and
testing process are interrelated, it is usually impossible to differentiate
these in a group of measurements. If the material composition and placement
process effects are combined into a material quality effect,, then;
6Q = 6M + 6p (3-8)
and
<5 = 6n + ^ (3-9)
42
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where 6 = correction for systematic error of the measurement process at
" the reference level UT, due to the material quality, the
combined effects of material composition and placement process
The testing process accuracy correction of Equation 3-7, 6 , can theo-
retically be reduced to zero for any testing process by suitable calibration.
However, as stated by Willenbrock (1976, p. 18.37), "A practical difficulty
in judging accuracy (of a test method) is that the only way to find the true
value is by some other method of measurement. Presumably, the method em-
ployed to determine the true value should be a method of high precision that
is believed to be without bias." The statistical aspects of calibration are
presented later in this section of the report.
Precision Error
The precision term of Equation 3-5, e, is a random effect, and is the
combination of random effects due to the three causes discussed above. The
statistical variance, a^, of a group of measurements of a characteristic of
a consistent material using a consistent test method is the sum of the
variance due to the three causes of random variability. This may be given
as*.
and defining
then
q - 4+ 4 (3-n)
4 (3-12)
where a. = overall variance
2
a = variance due to material composition
2
o_ = variance due to placement process
2
a = variance due to testing process
2
cr = variance due to material quality
If the standard deviation of a particular testing process, ay, is
known, or can be estimated, then its effect on the overall standard
deviation, aQ5 can be evaluated (Hald, 1952, p 217) from Equation 3-12 as:
43
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(3-13)
As Hald states t "On account of the uncertainty of the method of measurement,
the observed values have a standard deviation that is greater than that of the
true quality characteristic in question." For example, if the standard devia-
tion, CF.J, of the testing process is equal to, or 100 percent of, the quality
standard deviation, an, then the total standard deviation, CTQ, will be 41 per-
cent larger than OQ. On the other hand, if the testing standard deviation,
a^, is only equal to 20 percent of ag, then the total standard deviation, 0Q,
will be only 2 percent larger than the quality standard deviation, OQ.
When comparing alternative test methods, the effect of different standard
deviations of the test methods on the overall standard deviation should be
considered. For such comparisons the important conclusion that can be drawn
from the examples given above and from Equation 3-13 is that when material
quality is uniform (low CTQ) the precision of the test method (CT.J,) is of great
importance. However, when material quality is not uniform (high OQ) the
relative precision of one test method (CT^) versus another is of little overall
importance.
TYPES OF INSPECTION
Three major methods are available for the inspection of geotechnical
construction. These are (1) screening, or 100 percent inspection; (2) process
inspection (Enrick, 1972); and (3) block-by-block inspection sampling and
testing.
Screening, or 100 percent inspection, is often preferred to any other
type of inspection because it is the only way to be reasonably sure that all
substandard aspects of the work are detected. Of necessity, the testing must
be nondestructive and is usually accomplished visually. Examples are the
observation of site preparation, the visual examination of the exposed sur-
faces of cut areas (for site media verification), and for imperfections in a
geomembrane liner.
Process inspection is performed by an inspector who observes a construc-
tion process. His observations are concerned with all aspects of the work
including incoming raw materials, the workmen, the equipment, and the con-
struction process. His intent is to discover substandard construction and,
when it occurs, to initiate corrective action. Examples are observations of
proper equipment selection and operation, compacted lift thicknesses, and
uniformity of compaction for both coverage and number of passes.
Block-by-block sampling inspection uses the result of measurements on a
sample to judge the acceptability of the entire block. This method is appli-
cable to sampling performed for either (a) process control or (b) acceptance
sampling and testing. When used this method calls for a complete acceptance
sampling plan. A complete acceptance sampling plan, which should be included
44
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in the design specifications, defines the following (Willenbrock, 1976;
Miller-Warden Associates, 1965):
a. The quality characteristic(s) to be evaluated
b. The block size: a definite quantity of material or construction
specified for acceptance or rejection
c. Location(s) of sample units or measurements
d. Number of sample units or measurements per block
e. Sampling and testing procedure
f. Method of calculation and evaluation of data; treatment of
outliers
g. Acceptance criteria
h. Corrective action to be taken in the event of noncompliance
The various quality characteristics associated with geotechnical construction
processes at a hazardous waste disposal facility were discussed in Section 2
of this report. Commonly used techniques for performing tests for the quality
characteristics will be discussed in Section 4. The establishment of natural
process tolerances and selection of acceptance criteria are both design
functions, involving site-specific requirements and engineering judgment.
The actual physical means of corrective action, in the case of noncompliance,
is a combined design and construction operations function. Both of these
latter topics are beyond the scope of this report.
A block, as defined in this report, is a definite, isolated quantity of
soil, or otfier material, of the same composition and produced by essentially
the same process. It is characteristic of a block that all measurement
variation within it is random or assumed to be random, with no underlying
difference between locations in the block. Therefore, the block can be
characterized by a block mean and a block standard deviation for each quality
characteristic. Generally, materials and workmanship close together in time
or space will often be more similar than elements far apart. The size of most
practical size blocks is so much greater than a sample taken from it that
there is no relationship between sample size (area, volume or weight) and
block size. Therefore, the size of the block is established on the basis of
judgment of uniformity of materials and workmanship and on economics. (Block
size selection will be discussed in detail in Section 4.) Often, this is a
day's production, or a portion of a day's work, or a stockpile of material
from a well defined source, or a single shipment of off-site material. For
sampling, the block is usually subdivided into a large number of sub-blocks,
°r sampling units, each a small, easily identified length, area, volume,
weight, or time period.
45
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TYPES OF SAMPLING
Every block of material or of construction will have a frequency distri-
bution of measurement data similar to Figures 8 and 9 for any quality charac-
teristic. Regardless of its form, whether bell-shaped as in the given figures
or in some other common shape, its quality will be characterized by a central5
mean value and by random variation about the mean, defined by the standard
deviation. A sample increment is a portion of material, taken from a block,
for the purpose of inspection as a basis for judging, or estimating, the
quality of the block. That part of a sample increment actually tested is
called a test portion. The sample average is an estimator of the block
average and the sample standard deviation is an estimator of the block
standard deviation.
Representative Sampling
Single, representative (judgemental), sampling has been the traditional
engineering approach in construction inspection, based on a deterministic
attitude toward variability and the concept of the "representative" sample.
Willenbrock (1976) states, "Considerations in the past to staffing, sampling,
and testing time, as reflected through economics, probably guided (the tradi-
tional engineers) in this direction." Multiple sample locations, with the
sample increments blended into a single test portion, have been an attempt to
recognize variability and to test a sample representative of the whole, i.e.,
to test an "average" sample. Unfortunately, the single sample or the blending
process does not yield a sampling variance by which an estimate of the block
variability can be made. The judgemental selection of the sampling loca-
tion (s) is usually left up to the sampler or his superiors, making the entire
process dependent on the validity of his judgment, with its inherent tendency
toward bias.
As stated by Deming (1950), "Judgement samples...are not amenable to
statistical analysis." "...(there is) no way to remove the biases of selec-
tivity, availability, ..., and incorrect assignment of weights." "The
usefulness of data from judgement samples is determined by expert knowledge
of the subject matter and comparisons with the results of previous (inspec-
tions)..., not from the knowledge of probability. Such remarks are not meant
to imply that judgement samples cannot and do not deliver useful results, but
rather that the reasons why they do when they do are not well understood."
Judgement samples require a highly knowledgeable and experienced inspector.
On the other hand, probability samples do not rely on experience or judgement
of the sampler and can, therefore, be accomplished by less well trained
personnel.
Random Sampling
Whether intended or not, every sample used to estimate universe, or
block, parameters is a statistical sample. Its rational usefulness in this
regard depends on its randomness. The requirements for a random sample, as
given by Arkin and Colton (1950) are:
"1. The sample must be selected without bias or prejudice;
46
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2. The components of the sample must be completely
independent of one another;
3. There should be no underlying differences between
areas from which the data are selected; and
4. Conditions must be the same for all items in the
sample."
Statistical random sampling is essential for securing a sample to be used
to estimate the universe mean and standard deviation of the block. Random
sampling has been described by Hald (1952) in several designs:
a. Uniform random sampling
b. Stratified random sampling
c. Systematic sampling with a random start
d. Two stage sampling
Uniform Random Sampling
The uniform random sample makes every potential sampling unit in the
block equally likely to be selected. A table of random numbers is used to
establish the time or spatial coordinates for each sample unit. This form of
sampling provides an unbiased, representative estimate of material charac-
teristics. However, because of the small sample sizes normally used in
construction inspection, such a sample may not provide the complete coverage
of a block that engineering judgment demands.
Stratified Random Sampling
If a universe or block consists of, or can be divided into, a group of
sub-blocks or strata having different properties according to some specified
criteria, then a random sample can be drawn from each stratum instead of
drawing a single random sample from the entire population. This is called
stratified random sampling. The division of a soil mass or a construction
process into blocks is a form of stratified random sampling. The total sample
size is proportioned among the strata in accordance with their proportional
weight or area. Within a single block, the time frame or the area or volume
can be divided into a convenient number of sub-blocks, or sampling units, each
of a size expected to yield near uniformity. These may be a square yard, or a
100 ft square, or a 15 min sequence of time. Selection of sub-blocks to be
sampled, and the selection of locations within the sub-block to be sampled,
are by random methods.
Systematic Sampling
A popular sampling method is systematic sampling with a random start.
This method involves the selection of successive sample units at uniform
intervals of time, distance, area, or volume. It is argued that if the first
47
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sample unit is selected at a random location, then all successive units are
random also.
Two Stage Sampling
Two stage sampling is similar to stratified random sampling in that the
block is divided into a large number of strata and a random selection is
made of sample strata. Then a random sample of secondary units is selected
from each primary unit. This is useful when the primary units consist of
sacks, boxes, or similar containers, or the block can be arbitrarily divided
as though it were similarly contained. Deming (1950) and Hald (1952) dis-
cussed this method with respect to secondary sample size as a function of
the cost of securing a primary sample unit and the cost of sampling and
testing each secondary unit. The greatest efficiency, assuming costs are
the same, occurs in sampling only one secondary unit from each primary unit.
Example of Sampling
Probably the best method available to the engineer concerned about
sampling all parts of the block is a combination of (a) stratified random
sampling and (b) systematic sampling with a random start. By subdividing
each block into a convenient large number of sample units, using a random
start, and following a systematic pattern, a random sample with uniform
coverage of the block is obtained. Hald (1952, p. 490) and ASTM (1982)
Designation E 122-72, "Standard Recommended Practice for Choice of Sample
Size to Estimate the Average Quality of a Lot or Process", state that the
number of sampling units in a block should exceed lOn, or ten times the
sample size.
In random sampling, it is very useful to assign a consecutive number to
every sampling unit and to select among the units by some source of randomly
generated numbers. These include tables of random numbers found in many
statistics textbooks or a computer generated random number series. Games of
chance can be used, such as a roulette wheel or similar devices. Or a
series of numbered discs, placed in a bowl and thoroughly mixed, can be
used.
As an example of the various possibilities for random sampling, assume
the following:
a. An inspection block consists of one area 200 ft by 300 ft.
b. The use of 10 ft by 10 ft sampling units will be employed; this
gives a total of 600 sampling units with 30 rows and 20 columns
in the grid.
c. The individual sampling units are numbered, in a sequential
fashion, continuously from one to 600.
d. The location of the sample increment within a selected sample unit
will be chosen at random.
e. The necessary sample size equals six (n = 6).
48
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Then, there are several potential random sampling schemes that can be
adopted for selection of sample units to be sampled:
a. Select six units completely at random from among the 600
available.
b. With a random start among the first 100 units, take every successive
100th sampling unit.
c. With a new random start among the first 100 units each time, select
units at 0, 100, 200, 300, 400, and 500 added units on successive
starts.
d. From every 100 successive units, select one at random.
e. Moving along the 300 ft direction, select a row in the first
50 ft at random; select a column at random. Next, select a row
from the next 50 ft at random and select another column at
random, etc.
SELECTION OF SAMPLE SIZE
A statistically rational and valid method for selecting sample size is
given in ASTM (1982) Designation E 122-72. The equation for the number of
sample units (sample size, n) to include in a sample in order to estimate,
with a prescribed precision, the average of some characteristic of a block
is:
n = (ta'/E)2 (3-14)
or, in terms of coefficient of variation
n = (tV'/e)2 (3-15)
where n = number of units in the sample
t = a probability factor, from the Tables of Students'-t, based on
confidence level and sample size
a1 = the known or estimated true value of the universe, or block,
standard deviation
E = the maximum allowable error between the estimate to be made
from the sample and the result of measuring (by the same
methods) all the units in the block, i.e. the confidence
interval
49
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V = coefficient of variation = a'/X', the known or estimated true
value of the universe or block
e = E/X', the allowable sampling error expressed as a percent
(or. fraction) of X'
X' = the expected (mean) value of the characteristic being measured
The probability factor, t, in Equations 3-14 and 3-15 depends on
(a) the chosen level of confidence and (b) the size of sample used to esti-
mate
-------
TABLE 4. t-FACTORS FOR LARGE SAMPLES
t-
Factor
3.0
2.575
2.320
2.0
1.960
1.645
Probability of
One Sided
0.0013
0.005
0.010**
0.023
0.025
0.050
Exceeding E or e*
Two Sided
0.0026
0.010
0.020
0.046 •
0.050
0.100
* E or e defined in Equations 3-14 and 3-15.
** Probability of 10 in 1000, or 1 in 100.
the average percent compaction of the construction block. Redus and
Spigolon (1965) studied U. S. Army Engineer Waterways Experiment Station data
on compaction of low plasticity clay, with density expressed as a percent of
modified Proctor maximum density. The data yielded:
n = 172 tests
X = 91.1 percent of modified Proctor maximum
a = 2.0 percent of modified Proctor maximum
V = 2.19 percent
Using a confidence level of 99.5 percent (a probability of 5 in 1000 that
the error will exceed e), the t-factor from Table 4 is 2.575. If it is
desired that the error, e, in the average not exceed 2.0 percent of modi-
fied Proctor maximum, then:
n
["2.575 (2.19)1:
L 2.0 J
= 7.95, or 8 tests
Note that if the process coefficient of variation reaches 3.0 percent, then
for the same confidence level and maximum error, 15 tests will be needed.
If eight (n = 8) tests are used, then the maximum error in the block average
becomes 2.7 percent of modified Proctor maximum density lower than the
sample average.
Example 2: This is a two sided analysis. Assume that it is desired to
estimate the average water content of a layer of silt soil exposed in a
trench wall. The silt has previous data similar to that shown in
Table 3; that is:
51
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n = 406 measurements
X = 20.6 percent water content
a = 4.7 percent water content
Using a two sided confidence level of 99.0 percent (or a probability of 10 in
1000 of exceeding E) and a maximum error, E, of 5 percent water content,
either above or below the sample average, then?
f2.575(4.7)12 _ Q , ^
n = j~ = 5.9, or 6 tests
These tests, and those in Example 1 above, should be made on sample incre-
ments taken from their respective blocks using one or another of the random
sample designs described above.
A supposed advantage of the traditional, representative sampling method
is that it allows the inspection personnel to perform additional tests in
an area or block of work that has been deemed critical by the design
personnel. As can be seen from the above examples, the statistical sampling
methods can be used by the inspection personnel to provide for such a situa-
tion. By lessening the confidence interval for a block of work, the inspec-
tion personnel are provided with more confidence in that block of work's
acceptability.
Treatment of Outlying Observations
Occasionally, in a supposedly homogeneous sample, one of the test
results appears to deviate markedly from the remainder of the sample. Such
an observation is called an outlier. Assuming all mistakes are eliminated,
then two causes for the large deviation are of interest:
a. The outlier may be a natural occurrence of the extreme values
that have a very low, but finite, probability of occurrence. In a
normal distribution, such as shown in Figures 8 and 9, and using
the t-factors of Table 4, a single value has a probability of
1.3 in 1000 of deviating at random for the average by 3.0 a.
b. The outlying observation may be the result of an assignable
cause, a change in universe, even though we assume it is from the
same universe as the other observations.
Even though the first type of outlier is part of the random universe
and should be part of the sample, it should be rejected. The sample is as-
sumed to be representative of the universe. The presence of an outlier will
sufficiently modify the sample mean and standard deviation that the sample
is no longer representative and will lead to wrong decisions (Neville and
Kennedy, 1964).
52
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Criteria for rejection of outliers are based on the confidence level
concepts used in Equations 3-14 and 3-15. Recommended criteria are con-
tained in ASTM (1982) Designation E 178-80, "Standard Practice for Dealing
with Outlying Observations". The procedures used in ASTM Designation
E 178-80 are not difficult or complex, however, the discussion and tables
included in ASTM Designation E 178-80 are too extensive to quote in this
report, and the reader is referred to the document itself.
Calibration
Calibration is used to develop a relationship between the results of a
testing method and a reference standard over a range of test values. Measure-
ment of a quality characteristic can then be made using the test method and
the true, or reference, value as estimated from the relationship.
The use of a calibration involves two steps. First the relationship
is established, usually by a planned experiment, and a graph or mathematical
equation is derived to define the relationship. Then one or more repetitions
of the test method are made at a quality level, the results are averaged, and
the average entered into the graph or equation to be used to estimate the
true value. As will be shown below, the maximum error (confidence interval)
for the true value is a function of the sample size (number of data pairs)
used in the calibration experiment and of the sample size (number or repeti-
tions) during the measurement itself.
The following discussion is limited to the use of a statistical linear
regressions analysis, using the method of least squares, to fit the calibra-
tion equation to the experimental data. If the relationship is curvilinear,
a similar analysis may be found in most textbooks on statistical methods and
is beyond the scope of the report. A numerical example of the use of the
calibration equation is given below, following presentation of the mathemati-
cal equations.
Linear Regression Analysis
The theoretical development of the method of least squares is given in
most textbooks on statistical methods. These include Benjamin and Cornell
(1970), Hald (1952), Miller and Freund (1977), and Neville and Kennedy (1964).
The interested reader is referred to these texts for the derivations.
Linear regression analysis is used to evaluate a number of data pairs
(x,y) resulting from an experiment. In calibration, this usually results
from a test instrument being used to measure a range of values of a quality
characteristic whose true, or reference standard, values (x) are the inde-
pendent variable, while the measured values using the test device (y) are
the dependent variable.
Assumptions made in linear regression analysis, using the method of
least squares, are (Hald, 1952):
a. Values of x are either error free or subject to negligible error
only; they can be naturally occurring or predetermined.
53
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b. Values of y are normally distributed for all values of x.
c. The mean value of y corresponding to a given value of x is a
linear function of x.
d. The random error of y (variance of y) is constant for all values
of x or proportional to a given function of x. In the latter case,
transformation of variables will be necessary.
For a hypothetically infinite number of data pairs for the material and
test method(s) of interest, the linear relationship of y and x will bes
y = a + Bx + E (3-16)
where y = dependent variable
x = independent (error free) variable
a = intercept
g = slope
£ = random deviation in the y-direction of the y-value, at a specific
x-value, from its calculated value on the line
In an experiment of finite size, the method of least squares fits the
data with a straight line:
y = a + bx + £ (3-17)
in which the parameters are defined by
a = y - bx (3-18)
and
nZxy - Sxly
v 2 ,_ ,2 (3-19)
nEx - (Ex)
where a = intercept
b = slope
x = average of all x-values, Equation 3-1
7 = average of all y-values, Equation 3-1
54
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n = number of data pairs in sample
In many situations, particularly calibration, there is a tendency on
the part of the analyst to force the data to go through the origin, i.e.,
y = 0 at x = 0. It is recommended that this not be done. Because of the
limited size of most samples, a better fit is usually obtained by including
the intercept equation (3-18). Futhermore, there may actually be a systematic
error, the value of the intercept, present in all y-values, that should be
recognized.
The random variability of the line is given by:
(3-20)
Recognizing that, for any given value of x, the average value of the y's is
given by the estimate, a + bx, then:
s2 = Z[V - (a + bx)]2 (3-21)
e n - 2
The value, S , is called the standard error of estimate. The various
concepts described above are presented pictorially in Figure 10.
The purpose for establishing a calibration relationship is to permit the
use of measurements made using a particular device to estimate a true, or
reference, value. The validity of the measurement data can be stated in terms
of the maximum error, or confidence interval, that can be expected.
If, at a quality level x = x , the calibrated test device is used to make
K repeated measurements (K = 1,2,...) resulting in K values of y, and the
y-values are averaged, yielding y', then the estimated value of x is x1
given as:
x' - x + y' " y (3-22)
b
and the maximum error (confidence interval) is (Hald, 1952) :
S 'i + 1 + [(y' - y)/b]2
n , -2
N E(x - x)
where y' = average of K values of y from K = 1,2,... repetitions of
tests at the level of x = x
o
55
-------
Y
-STANDARD ERROR OF ESTIMATE Se
(±Se CONTAINS ABOUT 68 PERCENT
OF ALL VALUES) Se = y
Y VALUES ASSUMED TO BE NORMALLY
DISTRIBUTED OVER GIVEN INTERVALS OF X
____] I
a. CONCEPT OF STANDARD ERROR OF ESTIMATE
X
Y
UJ
_j
OQ
<
ir
RESIDUAL, (Y-Y'j
CONFIDENCE
INTERVAL
LU
LU
Q
CO
LU
D
Q
LU
tr
CO
bx,-,
EQUATION OF
REGRESSION LINE,
FIXED ATX, Y.
V ^- CONFIDENCE LIMIT
CONFIDENCE INTER VA L
MEASURED VALUES OF X, (INDEPENDENT VARIABLE)
b. CONCEPT OF LINEAR REGRESSION LOAD
Figure 10. Concepts of regression analysis.
56
X
-------
x' = estimated value of x
Using the same concept of maximum error (confidence interval) presented
earlier in Equation 3-14, the term E represents the maximum deviation of the
sample value from the universe value at the chosen probability level. A
two sided analysis is used since it is not known if the universe value is
larger or smaller than the sample estimate. The probability level, a (not
to be confused with the universe intercept, a), from Table 4 should be used
to define the probability that the calculated maximum error, E, will be
exceeded. Values of t from Table 4 should be used for calibration experi- -
ments with over 25 data pairs. For smaller sizes (n less than 25), tables
of Student's-t should be used; these are found in statistics textbooks.
The effect of sample size is reflected in the equation for maximum error
(3-23). The size of the sample, n, used in the initial calibration is
reflected in Equation 3-21 for the standard error of estimate and in Equa-
tion 3-23. Then the size of replicated tests, K, used when future values of
x are estimated, is reflected in Equation 3-23.
The-denominator within the radical of Equation 3-23 includes a term
£(x - x) , which is from the initial calibration. The error in Equation 3-23
can be reduced if this term is made large. This implies that, in the planning
of an experiment, such as a_calibration, the x-values be chosen as far re-
moved from the mean value, x, as possible. This is preferred to the more
conventional method of spacing test x-values evenly. Of course, this is also
dependent on the experimenter's prior knowledge that the x - y relationship
is truly linear. Even though two methods for testing for the same parameter
should be related by a 45 degree line through the origin; the sample relation-
ship, or even the universe one, may be curvilinear because of some quirk of
the apparatus or technique. This factor must be considered and investigated.
Example of Calibration
The linear regression Equations, 3-16 through 3-23, given above may be
applied to the evaluation of a calibration of, for example, an alternative
test procedure with a standard one. Benjamin and Cornell (1970, pp. 430 -
438) presented a scattergram of data pairs representing soil water content
determined on duplicate samples by the standard laboratory oven-dry proce-
dure (Method 1 of Appendix B) and by the calcium carbide (Speedy) moisture
tester (Method 5 of Appendix B). The calcium carbide method is rapid and
inexpensive and is well suited to field use. The purpose of the calibration
is to estimate the true, laboratory-derived water content given one or more
observed values of the rapid test. In this discussion, the data are
presented only for illustration and no assertion of validity is made by the
authors.
Sixty-seven data pairs of water content were recorded on soil samples
tested by both methods. Reversing the order used by Benjamin and Cornell,
the data are identified as:
x = Laboratory oven-dry water content (independent variable),
percent
57
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y = Calcium carbide (Speedy) water content (dependent variable),
percent
From the listing of paired data, the following values were calculated:
a. Sample size (number of data pairs) n = 67
b. Sum of values of x £x = 924.6
c. Sum of values of y Sy = 924.6
d. Mean values of x x = 13,8
e. Mean values of y y = 13.8
2
f. Sum of squares of values of x Zx = 13,291
2
go Sum of squares of values of y £y = 13,260
h. Sum of individual x times y Exy = 13,145
_ 2
i. Sum of squares of deviations of x I(x - x) = 490.44
2
j. Variance of y-values about line . S = 3.09
k. Standard error of estimate S =1.76
The equality of the means for x and y is merely a coincidence. Using Equa-
tions 3-18 and 3-19, the best fitting straight line to the 67 data points is:
y - 3=79 + 0.725x (3-24)
Equation 3-24 is theoretically valid only for the general soil type and the
water content range used in the calibration. The water contents ranged
from nine to twenty-three percent.
Next, assume that a sample of the same soil type is obtained, thoroughly
blended, and tested K times using the Speedy moisture tester, yielding an
average value, y', of 15.0 percent water content. Then, using Equation 3-22,
the estimated true value (laboratory oven-dry) of water content, x', is
15.46 percent. However, this is an estimate made using a test device that
is subject to random measurement error. The magnitude of the probable error
in x' as a function of K, the number of repetitions of the test, can be shown
by Equation 3-23.
Assume a confidence level of 0.90 and select a value of t = 1.645 from
Table 4. This implies that the probability that the maximum error will be
exceeded is 0.10. Then:
a. If K = 1, E(x') = 4.03 percent
58
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b. If K = 2, E(x') = 2.88 percent
c. If K = 4, E(x') = 2.08 percent
d. If K = 8, E(x') = 1.52 percent
Therefore, if this Speedy moisture tester were to be considered an alterna-
tive to the labotatory oven-dry method, the maximum error in the estimate of
x' can be reduced by repeating the test K times on the same sample of soil.
However, even if K is made a large number, E(x') converges on 0.57 percent
water content because of the inherent variability in the test device itself.
It must also be recognized that the actual error in most tests will be much
less than the maximum error.
The cost of repeated testing (K times) can, by this analysis, be com-
pared with its benefit in a more precise estimate of x'. Given similar data
for other devices, a cost comparison can then be made between the devices to
provide equal precision. Furthermore, if the maximum error (confidence
interval) for this test method, at a reasonable value of K, is or is not
acceptable within the scope of the quality assurance requirements of the
project, this factor can be experimentally established and documented as part
of the total project quality assurance program record.
-------
SECTION 4
TESTING
Section 2 of this report identified the geotechnical parameters that
should be observed or tested during the construction of a disposal facility.
For the purposes of this report, an observation usually does not involve
a formal or specific method, whereas a test almost always involves a specific
and consistent technique and often a specific piece of equipment. Standard
laboratory or field test methods exist for each of the soil engineering
properties and index properties that were identified and defined.
This section of the report identifies and describes the standard test
methods for the soil index properties. For most of these, there exist com-
monly used alternative test methods; these are also identifed and described.
Because observation techniques are normally nonspecific, they are described
only in general terms. The merits and limitations of the various observation
and test techniques, as used in a quality assurance program, are presented
and discussed. None of the commonly used test methods for the same index
property is clearly superior in all respects to any other test method for
the same index property. It is therefore concluded that any alternative
test method is acceptable, provided an acceptable calibration is made and
used also.
TEST AND OBSERVATION METHODS
The following discussion includes only those tests and observations that
were identified in Section 2 of this report. They are the ones considered
most appropriate for both process control and acceptance inspection during
construction. Although not discussed here, other tests may be used" for spe-
cial investigations during construction, but these are not usually performed
on a routine basis. These include such tests as the engineering properties
tests (see Section 2), geochemical tests, hydrology related tests, off-site
evaluations of off-site materials, and material specific tests of nonsoil
materials such as portland cement, asphalt, and others. The performance,
recording, reporting, and evaluation of these tests should be done in a
manner similar to that described below for the identified tests.
Soil Index Properties Test Methods
The listing given below includes the standard laboratory test method for
each of the index properties. In most instances, alternative standard or
nonstandard methods are in common use. There are undoubtedly other alterna-
tive methods for some of the tests that are used by various testing groups
60
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for construction control; however, they are not as well known, well docu-
mented, commonly accepted or as widely used as those described.
Appendix B contains a one-or-more page description of each of the test
methods listed below. In each instance, the following outline has been used:
a. Parameter measured:
Title of test method:
b. Principle of test method:
c. Test method
(1) Apparatus:
(2) Procedure:
(3) Reference:
d. Limitations:
e. Status of the method:
f. Calibration procedure:
g. Documentation of test:
The various soil index properties test methods and other test methods
included in Appendix B are:
Water content test
a. Standard oven dry method
b. Standard nuclear moisture-density guage method
c. Gas burner (frying pan) method
d. Alcohol burning method
e. Calcium carbide (Speedy) method
f. Microwave oven method
g. Infrared oven method
Unit weight test
a. Standard laboratory volumetric method
b. Standard laboratory displacement method
61
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c. Standard field sand cone method
d. Standard field rubber balloon method
e. Standard field drive cup method
f. Standard nuclear moisture-density guage method
Specific gravity test
Standard laboratory method
Grain-size distribution test
a.. Standard sieve analysis (+200 fraction) method
b. Amount of soil finer than No. 200 screen (wash) standard method
c. Standard laboratory hydrometer (-200 fraction) method
d. Pipette method for silt and clay fraction
e. Decantation method for silt and clay fraction
Liquid limit test
a. Standard multipoint method
b. Standard one point method
Plastic limit test
Standard laboratory method
Cohesive soil consistency test
a. Standard unconfined compression test method
be Field expedient unconfined compression test method
c. Hand (pocket) penetrometer method
d. Handheld Torwane method
Water content/density/compactive effort tests
a. 25 blow standard Proctor compaction method
b. 25 blow modified Proctor compaction method
c. Nonstandardized Proctor compaction methods
62
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d. Rapid, one point Proctor compaction method
e. Rapid, two point Proctor compaction method
f. Hilf's rapid method
g. Ohio Highway Department nest of curves method
h. Harvard miniature compaction method
Cohesionless soil relative density test
a. Standard laboratory maximum density method
b. Standard laboratory minimum density method
c. Modified Providence method
Geomembrane/Geotextile seam integrity tests*
a. Bonded seam strength method
b. Breaking strength method
c. Peel adhesion method
d. Air lance method
e. Vacuum box method
f. Conductivity method
Criteria for Test Method Selection
With the exception of the nuclear guage moisture-density test, the den-
sity part of volumetric field density tests, and field tests of liner mate-
rials, all of the standard test methods identified above require (a) procure-
ment of a sample from the field and (b) performance of the test in a
sheltered environment. This usually involves the availability of electric
power, a water supply, freedom from dust and vibration, and a degree of
control over temperature and humidity. These are conditions found in a
central testing laboratory, and are available only in a few well equipped
Haxo (1981) lists potential liner materials: compacted fine grained soils,
bentonite clay, asphalt, Portland cement, chemical soil sealants, sprayed
liquid rubbers, and geomembranes. Most construction quality tests are the
same as, or closely similar to, the tests described above for soil index
properties. Other, material specific observations and tests are too
specialized to be included in this report. Test methods are usually
available from the material supplier.
63
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construction site laboratories, commonly found only on large construction
projects. In response to this, and for the other reasons given below,
alternatives to the standard test methods have come into common use for
construction quality control.
The criteria for selection among these alternative test methods include:
a. Time; speed of testing and/or speed of obtaining test results; The
efficient use of men and machinery on a construction site demands
that the results of quality control testing be made quickly available.
Construction costs can be one or more hundred dollars per hour. As
an example, the cost of a more expensive but rapid test must be com-
pared to the total cost to the permittee of a slower test method.
The time required to obtain a field sample and return it to the
laboratory should be compared to the time (and cost) of a field test.
b. Accuracy and precision; A reasonable reproducibility of test re-
sults must be obtainable if the test operator or specific test
equipment is changed. The accuracy must be stable so that a
calibration correction can be made; and once made, can be relied on.
The precision must be such that a reasonable number of tests can be
averaged to yield the required maximum error (confidence interval).
c. Adaptability to field laboratory conditions; The absence of elec-
tric power, the absence of water, and/or the absence of environ-
mental controls can effectively eliminate certain standard test
techniques.
d. Adaptability to on-site use; For example, soil density is easily
measured in place by the use of the mechanical or electric instru-
ments of an undisturbed sampling method. Laboratory measurements
require substantial sample manipulation and expertise on the part of
the performing technician.
e. Equipment and personnel cost: A comparison can be made in terms of
the capital cost of test equipment, the relative operator cost, the
cost of field laboratory services, and the need for a rapid test
method. Expensive, automated equipment cannot be justified if less
costly apparatus will provide equivalent results in sufficient time
for effective action, especially during small, slow moving construc-
tion processes.
f. Simplicity and ruggedness of equipment; An acceptable precision and
sensitivity of equipment can often be achieved with apparatus that
are simpler to use and more durable under field conditions than more
sophisticated devices. The degree to which an operator has been
trained, and his fatigue and/or boredom can seriously affect the
repeatability of a test method.
g. Nondestructive testing; This is of particular importance where the
act of sampling causes a discontinuity that must be repaired. For
example, securing a test specimen from a geomembrane requires
64
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placement of a secure patch to maintain the integrity of the
liner.
Observation Techniques
The observations identified in Section 2 are not dependent on the spe-
cifics of a particular technique. Most involve visual evaluations, or sim-
ple counting and tabulation, or are simple length or thickness measurements.
The usual procedures for these observations are either straightforward,
requiring no special instructions or equipment, or they involve visual com-
parisons that are either site specific or material specific. Therefore, any
attempt to establish standardized methods would be inappropriate in this
report. Specification writers and permit writers should simply state the
desired end result and leave the determination of technique to the experi-
ence and ingenuity of the inspector or his supervisor.
As an example of the statements made above, the smoothness and freedom
from sharp objects of the soil surface to receive a geomembrane can only be
accomplished by a 100 percent visual inspection. This is also true in the
observation for freedom of the placed membrane from tears. The thickness
of a soil lift prior to compaction can be quickly and reasonably well checked
by the performance of a number of measurements with a marked rod, or even a
suitably marked spade. The observation of a freshly cut trench wall or floor
starts with visual inspection for texture and color patterns, supplemented
by field expedient soils tests using the visual manual procedure. Sampling
and testing plans for site media verification studies can then be effectively
made. The results of the observation depend more on the quality of the in-
spector than on any specific details of technique. Desirable qualities of an
inspector are experience, integrity, technical experience and willingness.
Block Size and Testing Time
The determination of the size of a block, as stated in Section 3, is a
matter of economics rather than statistical analysis. From the statistical
viewpoint, the block should be sufficiently homogeneous that a reasonable
number of random samples can accurately characterize its properties. From
the economic viewpoint, the block size should be optimized to strike a
balance between the benefits derived from continuity in the flow of con-
struction and the benefits derived from avoiding the inherent costs of
block rejection for substandard quality.
Antrim et al. (1970) discussed this matter for a fairly continuous
production operation such as on a highway project. They indicate that the
size of a block depends on the type of construction. Block size will be
influenced by production rate, test time, and the time of analysis of data
to arrive at a decision. Sampling and testing for acceptance can only be
performed on the completed work, or else continued work will modify the data.
Therefore, using the notation of Antrim et al. (1970) and assuming the
maximum delay for a decision is equal to the time required to produce one
block (unless testing is done overnight), the minimum block size is given by:
N = PR(£TR + TD) (4-1)
65
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where N = number of units in block (such as square yards of fill
per one lift)
PR = production rate (units/time)
ET_. = total test time
R
1 = decision time
In Equation 4-1, the production rate is usually known and the decision
time is independent of the test method used. Therefore, the economical, or
efficient, block size will be a function of testing time.
From the statistical standpoint, as given in Section 3S there is no
mathematical relationship between block size and n, the sample size. If
it is desired that construction proceed at an unimpeded rate (assuming an
alternate work location during test and decision time) , then the maximum
average time for an acceptance test, from Equation 4-1, is given by;
where T = maximum average time for a test, in hours
K,
Q = production rate, in blocks per hour
J-j
T = decision time required to analyze data and arrive at a decision
to accept or reject the block
n = sample size; the total number of test increments in the sample,
from Equations 3-14 or 3-15
As an example of the use of these equations, consider the following
case. The fill placement crew can place and compact about 500 cubic yards
of liner soil in one half day. This is a single 6 inch lift in an area
about 100 ft by 300 ft. Assuming one 500 cu yd block per 4 hours, then QL
is 1/4 block per hour. If the conditions for Equations 3-14 or 3-15 require
8 randomly placed field density tests per block and it takes about 15 min-
utes to compile the data from the eight tests, analyze it, and arrive at a
decision, then n = 8 and T = 1/4 hour. Solving Equation 4-2:
= 0.47 hours, or 28 min
Therefore, the maximum average time for a field density test should not
exceed 28 minutes. If this cannot be achieved with the test method being
used, then four options are available:
a. Change to a test method that will give a testing time within the
required one.
b. Lower the number of tests per block; this will have the effect of
increasing the probability of exceeding the maximum error used in
Equations 3-14 or 3-15.
66
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c. Increase the size of the block, in effect reducing Q , the produc-
tion rate in blocks per hour; then, the risk of rejecting a larger
block must be justified.
d. Increase the number of crews using the test method so that average
testing time will be reduced; the increased cost and the possibil-
ity of increased testing variance must be justified.
The discussion presented by Antrim et al. (1970), is of limited
application in the determination of block sizes in the construction of a
hazardous waste disposal facility, as Antrim et al. (1970) address consider-
ations for a fairly continuous production rate. The construction of a
hazardous waste disposal facility will probably be (a) disjointed at times
and (b) lacking consistent continuity for its entire duration. Hence a
more encompassing method of determining block size, one that specifically
addresses the considerations for the construction of a hazardous waste
disposal facility, is needed. The authors recognized this need and developed
the following method.
Authors' Recommended Method for Block Size Determination
As has been stated, sampling and testing for acceptance can only be
performed on completed work, for continued work on the same block will
modify the data. This sampling and testing often causes interruptions in
the work (See Criteria for Test Method Selection, earlier in this section).
These work interruptions are necessary to assure that theT'designed-for
standard of quality is achieved. However, given the considerable costs
involved, considerable thought should be given to the schedule of these
interruptions, i.e. block size.
The flow of construction is the relative continuity and larger scale
operation of- construction at a specific facility. This flow of construction
is an abstract concept. But construction experience and the economy of scale
help to illustrate this concept. Construction worker competency and task
efficiency are improved through repetition. Literally, practice makes perfect.
Supervisor effort can be optimized when a supervisor directs the efforts of
several workers performing like tasks concurrently. It is generally more
cost effective to buy and transport materials in bulk. Generally, rental
costs per item of equipment lessen as the amount of equipment, rented at one
time from the same outlet, increases. Conversely, worker attention and task
efficiency suffer from frequent work stoppages. The frequent cranking on and
turning off of equipment wears heavily on that equipment. Peacemeal procure-
ment practices are generally cost ineffective. There are innumerable other
examples to illustrate the concept. They all serve to show that the permittee
can reap economic benefit from enhancing the flow of construction. This flow
of construction and the economic benefit derived from its enhancement are
depicted in Figure 11.
Given that the benefit of enhancing the flow of construction has been
presented, it should be clearly stated that the designed-for standard of
quality must be achieved everywhere and never compromised. From an economic
viewpoint, these two motivators: (1) enhancing the flow of construction
67
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BLOCK SIZE
This curve reveals the economic advantage of increasing
the block size. The curve can generally represent the
plots for the values of
FC '
W
or
ICO
BLOCK SIZE
This curve shows that for block size independent sampling,
P increases almost linearly till it approaches the 100%
R
line.
Figure 11. Graphic representation of important values
for the authors' recommended method
68
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and (2) achieving the standard of quality, appear to be conflicting. However
a compatible balance can be struck between them, and this is the object
of the authors' method.
The following points form a necessary preface to the presentation of
the authors' method:
a. For any given construction process there may be one or more quality
characteristics to be verified, i.e. sampled and tested.
b. A block size must be sufficiently large to allow statistical
sampling, as per Section 3, to verify each quality characteristic
within the block.
The following values are defined as indicated:
a. C This is the cost of the materials and workmanship that go into
the effort of construction. (Wherever it is used the word cost
means all the costs involved, i.e. including time, money and
intangibles such as the loss of worker attention.)
b. C This is the cost of inspection, that is the cost of the quality
inspection plus the cost entailed in the stoppage of construc-
tion in order to accomplish the inspection. The cost of
inspection can also be considered the worth of inspection.
This is because a block of construction, for which a quality
inspection has been performed, is intrinsically of more value
to the permittee than was that same block of construction
before the inspection was performed.
c. Cr This is the total cost of construction, that is the cost of the
. materials and workmanship plus the cost of inspection, so:
Cc = Cw 4- C]. (4-3)
d. CT This is the cost of the lost materials, workmanship and
inspection when a block of work is rejected, so often:
CL - CW1 + CI1 - CC1* (4'4)
e. C This is the cost of removing a block of construction.
£. CR This is the cost of rejection, that is the total cost when a
block of work is rejected, so:
CR - CL + CX + CC2 <4-5>
g. PR This is the probability that a block will be rejected. The
probability of rejection can only be estimated by the
* The number 1 indicates that this was the first time this work was
accomplished. Naturally, the number 2 indicates the second time.
69
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permittee's forces. They must use all their experience,
particularly the on-site experiences of the inspectorss to
estimate P . The value of P used should be the probability
that any quality characteristic tested will be found unac-
ceptable. The addition law of probability should be used to
calculate the probability of non-acceptance for a group of
quality characteristics to be verified.
h. D This is the deterrent or risk of rejection, that is the
probability of rejection times the cost of rejection, so;
DR = PRCR (4-6)
i. BSO This is the optimal block size.
j. BS This is the minimum block size possible which allows statisti-
cal sampling of each quality characteristic within the block.
To determine this value, one must first determine a minimum
block size for each quality characteristic within the block.
Then from among these minimum block sizes the largest is chosen
to represent the BS^ for the entire block. This entire
determination will usually be a moot effort as will be
discussed later.
k. F This is the flow of construction, an abstract concept
defined earlier.
An elementary risk analysis, as depicted by Figure 12, shows that the
optimal block size is located where the cost of construction exactly equals
the risk of rejection, so;
BSQ @ Cc = DR (4-7)
And if the value of BS0 exceeds the value of BSg then the value yielded by
Equation 4-7 is the block size the permittee should use for economic
optimization while assuring quality. (This will almost always be the case.
The authors can only conceive of extremely rare instances when BSg might
not exceed BSg. Conversely, it is more likely that BSg will exceed the maxi-
mum block size which still allows inspection. In this event the statistically
valid, maximum block size becomes BSQ' An example of this event would be the
compaction of earthfill over a very small trench. Each lift, or completed
block of work, must be inspected before the next lift can be compacted.) If
BS0 does not exceed BSS, then BSS is the block size the permittee should use
to assure quality.
It should be noted that if the permittee's forces miss in their estimate
of PRs their miss will manifest itself. The economic motivators of enhancing
the flow of construction and minimizing the cost of block rejection will
encourage the permittee's forces to redetermine a value for PR, yielding a
new block size closer to the optimum.
Experienced construction supervisors might be tempted to reject this
70
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BLOCK SIZE
There can exist a point at which an increase in the block
size means that inspection (sampling and testing) can no
longer be performed. This discontinuity is not represented
in the figure for the sake of simplicity.
BLOCK SIZE
The relationship between the values can be better visualized
if the values for C , C , and P are assumed to be
U K K
linear, i.e. C' , C' and P' . Note that once P' equals
v> K K |\
100%, Dp = C'
i\ K
Figure 12. Graphic representation of the solution of BS
0
71
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method as too complicated. In fact it is not. In fact it delineates clearly
what many construction supervisors attempt to do in their head. It also
calls for their experience in the estimate of PR. The other values needed
are readily determined. And the method serves to minimize the effects of
human error.
Once BSo has been determined for a given construction process, then it
is a logical next step to determine the total number of blocks to be
inspected for that particular process. In this way this method also helps
both the construction and inspection groups organize their effort.
Examples of the Authors' Recommended Method
The following examples demonstrate the utility and flexibility of the
authors' recommended method.
a. Example 1. At a given hazardous waste disposal facility one of the
landfill units has been filled with waste. The earthfill over the
waste must be compacted preparatory to the construction of a
trench cover. The trench itself is 500 ft by 200 ft.
The compaction crew supervisor knows that it costs approximately
$2.20 per cubic yard of compaction. This cost includes the costs
of the compaction equipment and its fuel, the labor costs of the
compaction crew and the quality assurance inspectors observing the
compaction, and all associated costs.
The compaction crew supervisor knows the cost of removing a lift of
compacted earthfill. Should the quality assurance inspectors find a
lift of compacted earthfill to be unacceptable and should those same
inspectors determine, along with the supervisor, that the lift must
be removed, it will cost approximately $1.50 per cubic yard.
The compaction crew supervisor also knows that in a given nine hour
day, with about an hour off for lunch and breaks, that his crew can
compact about 1,000 cubic yards. He also knows that lengthy stops
for his crew hinders their efficiency. It takes them time to get
back to their normal work rate.
The two quality assurance inspectors know that they cost approximately
$30 per hour, as a team, to perform their sampling, testing and
evaluation of a completed block of compacted earthfill. They also
know that it takes each of them approximately 15 minutes to take,
test and evaluate a given sample.
The quality assurance inspectors use a statistically valid, random
sampling method (as described in Section 3) to determine the sample
size for the completed block of compacted earthfill to be tested.
The sample size is eight.
The quality assurance inspectors know the importance of their work.
They also understand the concerns of the compaction crew supervisor.
72
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They decide to work with the supervisor to find the optimal block
size.
The inspectors and supervisor know from previous experience, and
from the trend that has been established at this hazardous waste dis
posal facility, that one unacceptable test result is found for every
250 cubic yards of compacted earthfill. They also decide that,
given the authors' recommended method, the work stoppage factor with
which the supervisor is very familiar will be given a value of 1.2.
The following list summarizes what the quality assurance inspectors
and the compaction crew supervisor feel are the appropriate values
to be used in the authors' recommended method.
3
(1) Compaction costs = $2.20/yd
3
(2) Removal costs = $1.50/yd
3 3
(3) Compaction crew rate = 1000 yd /day or 125 yd /hr
(4) Number of inspectors = 2
(5) Sampling costs = $30/hr
(6) Sampling time = 15 min/sample or .25 hr/sample
(7) Sample size = 8 samples
3
(8) Probability of unacceptance = 1/250 yd
(9) Work stoppage factor = 1.2
The following values were defined earlier in the presentation of
the authors' recommended method. Here they are shown in terms of
their units of measure:
cost of construction
\ /,-,,. . .
J x (block size in units)
stoppage factor) * x (tot,! sailing ti«e)]
/cost of removal \ , ... .
= I - tinit - / X vremoval Slze ln units)
_ /estimate of unacceptable test resultsN /, , , . . .
- I - un±i - / X ^b;!-ock Slze ln units)
73
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Replacing the word descriptors with variables and actual working
units reduces these definitions, or equations, to the following:
units) » $(a)(b)
samples) (d^hrs/sample) = (f
x (m units) =
PR "
The quality assurance inspectors and the compaction crew supervisor
can solve for their optimal block size by assigning the above
variables the values upon which they agree:
(1) a = $2.20/yd3
(2) b = optimal block size
(3) c = 8 samples
(4) d = =25 hr/ sample
(5) e = 2
(6) g = $30/hr
(7) h = 1.2
(8) j - 1 hr/125 yd3
(9) k = $1.50/yd3
(10) m - b*
(11) n = 1/250 yd3
* The quality assurance inspectors and the compaction crew supervisor know
that statistical validity dictates that an unacceptable test result will
mean complete block removal.
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Given these values the following equations result:
C = $(a)(b) = $2.20(b)
f . ISH.251
= $(1)(30) + ' = $3° + $33° = $36°
Cv = $(k)(m) = $1.50(b)
A
w = 0.004(b)
K.
Now the optimal block size can be determined:
Cc = Cw + GI (4-3)
Cr = $2.20(b) + $360
Given the assumption that an unacceptable test result means complete
block removal or loss:
(4-4)
CT = $2.20(b) + $360
Li
CR = CL + CX + CC2
C_ - $2.20(b) + $360 + $1.50(b) + $2.20(b) + $360
K
C_ = $5.90(b) + $720
K
DR = PRCR
D., = .004(b)[$5.90(b) + $720]
K
D- = $.0236(b)2 + $2.88(b)
Ix
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BSQ @ Cc - DR (4-7)
$2.20(b) + $360 - $.0236(b)2 + $2.88(b)
2.20(b) + 360 = .0236(b)2 + 2.88(b)
0 = .0236(b)2 + .68(b) - 360
Using the quadratic equation to solve for bs the unknown value, .equal
to the block size:
x =
-b + \b2 - 4ac
la
-•68 ± \(-.68) - 4(.0236) (-360)
b - 2(.0236)
-.68 + /.4624 - (-33.984)
b = __
-.68 + 5.869
.0472
Solving for the real solution gives:
b = BSQ = 109.9 = 110 yd3
So in order to optimize the flow of construction while assuring the
standard of quality, the compaction crew should compact 110 cubic
yards of earthfill at a time before stopping to allow the quality
assurance inspectors to conduct acceptance testing.
b. Example 2. Assume that the quality assurance inspectors and the
compaction crew supervisor in Example 1 are very confident that they
will always achieve a moisture content in their compacted earthfill
at or very close to the optimum moisture content. Assume that it
follows that they believe the only remedial action they will require
in the event of an unacceptable test result will be the application
of more compactive effort. Thus the inspectors and supervisor con-
clude that they will never have to remove a block of compacted earth-
fill in the event of non-acceptance.
From experience, and from the trend established at the facility, the
inspectors and the supervisor decide that the time required for the
typical number of remedial compactive effort passes is approximately
one half hour per 200 cubic yards of compacted earthfill involved.
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Thus the changed values from Example 1 are:
cx=o
3
Cro = [(remedial compactive effort rate: hr/yd )
u
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BSQ @ Cc - DR (4-7)
$2.20(b) + $360 = $.00275(b)2 + $1.44(b)
0 = $.00275(b)2 - 0.76(b) - $360
0 = .00275(b)2 - 0.76(b) - 350
Solving for b, the unknown optimal block size, by the quadratic
equation yields:
BSQ = 525 yd3
As was stated in Example 1, the trench size is 500 ft by 200 ft. If
the compaction crew is compacting in 6 inch lifts, then one lift over
the entire trench would be 5,556 cubic yards of fill. Thus there
should be 10.6, or approximately 11, blocks of compacted earthfill in
every lift over the entire trench.
c. Example 3. A geomembrane will be installed as part of the cover for
the trench being filled in Examples 1 and 2. The inspector and the
geomembrane installation supervisor determine the following values :
(1) Sample size = 18 samples
(2) Sampling time = 15 min/sample or =25 hr/sample
(3) Number of inspectors = 1
(4) Sampling costs = $12/hr
(5> Seam bonding costs = $45 /hr
(6) Seam bonding rate = 8 ft/hr (initial QC is performed in conjunc-
tion with the installation)
(7) Repair costs = $45 /hr
(8) Repair rate = 30 min/ft or .5 hr/ft
(9) Seam = 700 ft
Thus the following values can be assigned:
(2) b = optimal block size
(3) c = 18 samples
(4) d = .25 hr/sample
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(5) e = 1
(6) g = $12/hr
(7) h = 1.2 (again)
(8) j ='l hr/8 ft = .125 hr/ft
(10) m = b
(11) n = 1/29 ft
Given these values the following equations result:
C = $(a)(b) = $5.63(b)
£. 08K.25I
= $(4. 5) (12) + '> = $54 + $243'22
CX=°
PR = (n)(b) = .0345(b)
Now the optimal block size can be determined:
Cc - Cw + GI (4-3)
C_ = $5.63(b) + $297.22
c
CT = o
Li
CC2 = (k)(m) + CI = $22»5°(b) + $297.22
CL + CX + CC2
C., = $22.50(b) + $297.22
K
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°R = PRCR <4~6>
D_ = .0345(b)[$22.50(b) + $297.22]
K.
DB = $.776(b)2 + $10.25(b)
K
BSQ @ C(, = DR (4-7)
$5.63(b) + $297.22 = $.776(b)2 + $10.25(b)
0 = .776(b)2 + 4.62(b) - 297.22
Solving for b, the unknown block size, yields:
BS = 16 feet 10 inches
So there will be approximately 42 blocks of work in the bonding of
the 200 ft seam of geomembrane.
COMPARISON OF ALTERNATIVE TEST METHODS
The following discussion of the merits and limitations of the test
methods listed earlier relates primarily to the construction operations at a
hazardous waste disposal facility. All of the considerations presented here
with regard to standard test methods, alternate test methods, sampling,
calibration, and relative merits are applicable regardless of the mechanism of
the quality assurance program being employed.
Alternatives to the standard test methods may be acceptable if;
a. They measure the same fundamental property as the standard method;
or they correlate well with the standard test results.
b. There is a consistent relationship with the standard, i.e., a
consistent bias or accuracy error or constant calibration error.
c. The test precision is constant, and is known or may be estimated, so
that the maximum random error of a single or replicated test may be
evaluated.
Water Content Test Methods
Three different methodologies are in common use to determine the water
content of a soil during construction control:
a. Drying methods: These involve the removal of free water by a drying
process and comparing the weight loss, presumed to be water, with
the dry weight of the soil. The methods include standard oven
drying to constant weight at 105°C, pan drying over a flame or other
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heat source, drying by use of hot air, drying by an infrared radia-
tion source, or drying by a microwave oven. The alcohol burning
method uses the heat, from the burning of alcohol added to the
soil, to dry the soil.
b. Chemical methods: The most popular of these is the Speedy moisture
method using calcium carbide. The chemical is added to the wet soil
in a closed container and the pressure of the acetylene gas which
is produced is proportional to the free water present.
c. Nuclear methods; The nuclear moisture-density guages are commonly
used on projects of all sizes. They rely on neutron thermalization to
indicate hydrogen content.
A number of comparative evaluations of water content test methods have
been published. They include Shaw and Arble -(1959), Johnson and Sallberg
(I960), Schwartz (1967), Antrim et al. (1970), Smith (1970), and Schmugge,
Jackson, and McKim (1980). All are in general agreement in their evaluations.
Oven drying to constant weight at 105°-110°C is the long-accepted standard
method, using a controlled temperature oven. However, Lambe (1951) reports
experimental data to show that typical laboratory ovens are nonuniform in
temperature and will give slightly variable water content results. A study
by the Waterways Experiment Station (USAE, WES, 1954) showed that, for soils
containing gypsum, some of the bound water is evolved at temperatures below
105°C, affecting the results.
The distribution of water content throughout a soil sample is generally
nonuniform because of the nonuniformity of the percent fines, particularly
percent clay sizes, throughout. In a density sample of 2000 to 3000 grams
total weight, there are a number of 100 gram water content samples that can
be tested by .the oven drying method. Unless the soil is thoroughly blended,
the average water content will not be measured by the small sample. If water
content is used to establish the dry density of a sample, then the entire
sample should be dried; this then requires a large oven if a number of density
tests are to be made in one day.
All alternative water content test methods require calibration with the
standard oven dry method. The criteria given above require a stable calibra-
tion; this usually requires a consistent test technique.
The gas burner (frying pan) method uses an uncontrolled temperature to
dry the soil, with temperature often above 110°C. The Waterways Experiment
Station (USAE, WES, 1954) report showed that wide variation in temperature
above 110°C had negligible effect on low plasticity soils and only moderate
effect on medium plasticity soils. However, because the temperature is un-
controllable, the results are likely to be highly variable. The maximum
errors should be small at low water content, resulting in small errors in
associated values such as dry density or the Atterberg limits. The gas
burner method requires shelter, but no electricity or water.
The infrared radiation, hot air blower, and microwave oven methods
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offer some improvement over the gas burner method, but they require electricity
in addition to shelter. The testing time can be controlled and the test
apparatus standardized, offering the possibility of more stable calibration.
The alcohol burning method has a safety hazard in the open flame result-
ing from the combustion of the alcohol-soil mixture. All of the comments
given above for the gas burner method apply to this method. It also requires
a source of expendable alcohol. Since this method has no advantage over the
gas burner method, and is more unstable in calibration than the various
cooking methods, its use cannot be recommended. It is no longer commonly
used on construction projects.
All of the methods described above require testing times of 30 minutes
to several hours, with the exception of the microwave oven. This is a dis-
tinct advantage over standard oven drying which requires eight to 24 hours to
reach constant weight. Unless, of course, the time delay does not measurably
delay the construction operation.
All of the drying methods require that the soil test portion be
brought in from the field and dried in a protective shelter. This requires
manpower time for travel and causes the test technician to be away from the
construction site. The calcium carbide (Speedy) method is adaptable to on-site
testing, particularly if the shelter of a vehicle is available for the
weighing of the 26 gram sample of wet soil. The entire test can be completed
in ten minutes or less. The cost of the apparatus is a few hundred dollars
and the expendable calcium carbide costs only a few cents per test. Schwartz
(1967) reported a calibration standard error (Equation 3-20) of 1.44% water
content, so that most test values should be within one percent of the oven
dry water content. The apparatus is rugged and well adapted to field opera-
tion. Since there is no appreciable heat evolved and only the free water
combines with the calcium carbide, the presence of organic matter and/or
gypsum is not of concern, as it is in the drying methods. However the small
sample size, 26 grams, limits the method to fine grained soils. Also, the
soil must be thoroughly blended if the small sample is to be representative
of the average water content of a larger soil test increment.
The nuclear moisture-density apparatus costs several thousand dollars
and can be used for both water content and density tests in the field. Four
to six moisture-density tests can be performed continuously per hour by one
man. The tests are nondestructive and, therefore, can be repeated as a
replication or as a check for consistency. The tests can be made on any
flat surface, whether horizontal or inclined. Although the present day
instruments are fairly rugged, the electronic components have some drift, re-
quiring periodic recalibration. Because the guage responds to all hydrogen
present, including that in organic material and crystalline water, it is
necessary that a field calibration check be frequently made against oven -dried
soils. Under normal operating conditions, the instrument poses no health
hazard. However, formal operator training and a state license are normally
required.
In summary, all of the methods discussed above are viable, reasonable
alternatives to the standard oven drying method, provided, of course, that
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there can be a consistent calibration with acceptable precision. In opera-
tions where the moisture content samples can be obtained during the day's
work, and dried in the oven overnight, only a minimum of technician time will
be required; and the oven drying method can be recommended.
The alternative drying methods require 30 minutes to a few hours of
drying time for a single sample or a small group of samples. This time re-
quirement of an inspector/technician would make him unavailable for field
observations, thus possibly requiring an additional inspector. This is
undesirable, for labor is by far the highest cost item in inspection. Therefor,
unless the work schedule is so slow and intermittent that one inspector can
perform the field observations and also devote considerable time to laboratory
tests, the drying methods cannot be recommended.
The calcium carbide (Speedy) method may be used in the field or in the
laboratory, with results obtained in 5 to 10 minutes. It is applicable to
nearly all the soil types that would be encountered at a disposal facility.
With this method, thorough mixing of the soil is necessary to obtain a meaning-
ful representative test portion of 26 grams.
The nuclear moisture-density guage can only be used in the field on a
large soil mass. Small laboratory samples from Atterberg limits testing or
from compaction tests cannot be tested with this device.
Both devices, the Speedy and the nuclear guage, are sufficiently rapid
that the inspector can use them for process control and for acceptance testing
without adversely affecting construction efficiency. They are therefore
recommended for inspection testing intended to enhance the flow of construction.
Unit Weight (Density) Test Methods
The two laboratory methods for unit weight tests, volumetric and dis-
placement, are not generally considered process control tests. Both are time
consuming and require a laboratory environment.
In the volumetric method, the careful trimming of a soil mass into a
container of known volume or to a specific cylindrical diameter in a soil
lathe, or careful coverage with parafin or wax, requires skilled laboratory
technicians. The volumetric method is often used to prepare specimens for
other tests, such as unconfined compression tests or laboratory permeability
tests to be made on larger undisturbed field specimens or specimens of com-
pacted soil prepared in larger molds.
A large number of studies evaluating field density test methods have been
published, mainly in the journals of highway engineering. Typical of these
are the papers by Johnson and Sallberg (1960), Schwartz (1967), Winterkorn and
Fang (1975), and Antrim et al. (1970).
The four most widely accepted field density test methods are used pri-
marily for compaction evaluation. Three are direct techniques involving re-
moval of soil from the test site, weighing the removed soil, and measuring
the volume of the hole. These three: sand cone; water balloon; and drive cup;
differ only in their methods for measuring hole volume.
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The sand cone method depends on a calibrated sand density developed by
dropping through the valve of the apparatus cone. Unless the hole depth is
constant and the same as that used for calibration, a small bias error is
introduced. Vibration of the site by nearby construction machinery can
densify the sand during the test, introducing another possible error. The
sand is generally not reusable, requiring frequent resupply. A balance, of
sufficient capacity for weighing the sand filled apparatus, is needed. This
balance is usually different than the smaller balance used for the moisture
content tests by drying. The sand cone method can be used for the full range
of soils expected at a disposal site.
The rubber balloon method measures the hole volume by the forcing of a
water filled rubber balloon into the hole, with an apparatus used to measure
the change in water volume. As long as sharp stones or pieces of wood or
roots are not encountered, the balloon has a reasonable service life in spite
of its thinness and flexibility. The water and rubber balloon are sucked out
of the hole and reused, obviating the need for resupply. The rubber balloon
system will fit any hole well unless the hole is highly irregular in shape or
unless it contains root matter. In these latter two instances an error of
significant magnitude can be created.
In the drive cup method, a thin walled, steel tube is driven into the
soil. The soil must be fine grained and sufficiently yielding so that the
tube is not distorted. The soil filled tube is then dug out of the ground,
its ends are carefully trimmed, and it is weighed. With the volume of the
tube known, the soil density can be calculated. This method cannot be used
in sand, or in a soil containing stones. Another potential source of error
results when the soil is slightly compressed by the volume of the steel tube
walls and the wall friction developed during sampling.
All three of the direct methods discussed above require two steps:
(1) the hole is dug or the tube driven and removed; then the volume of the
soil is measured; and (2) the soil removed from the hole is weighed and the
wet density, or weight per unit of volume, is calculated. The determination
of the soil's dry density requires that the water content be determined by
one of the methods described earlier. In acceptance testing of a construction
block, such as for a lift of fill, a number of density tests are performed
at one time. This allows a partitioning of the work. All the field work can
be performed at one time. This is then followed by a transport of the pro-
tected samples to the field laboratory for their weighing and subsequent mois-
ture determination. This method becomes cumbersome for process control work
when only one or two tests can be made at a time. In this situation, all the
weighing and moisture determination should be performed on site, or else
there will be a loss of time, and a loss of inspector observation capability
while he is working in the laboratory. Each of these test methods requires
15 to 45 minutes of field work, followed by additional- laboratory time.
A skilled technician can perform eight to ten tests, density and water
content, in a day.
The nuclear moisture-density guage uses gamma ray attenuation to measure
the total, or wet density. All of the comments made earlier in the Water Con-
tent Test Method subsection of this report apply equally to the measurement
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of density. The two tests, water content and density, can be made in five
to ten minutes with a single positioning of the nuclear guage. In the pre-
ferred direct transmission mode, all of the soil between the source and the
detector is tested. If the source is at the bottom of a compacted soil lift,
then the guage measures average lift density at the test location. Water con-
tent, on the other hand, is usually measured in the backscatter mode. There-
fore, the water content of the uppermost one to two inches of the soil mass
contributes most of the measurement. If there is a moisture gradient or dis-
continuity in the soil mass to the depth of the probe, an error in dry den-
sity calculation will be made. For this reason, the test should always be
made on a freshly cleared surface (as described in the instrument's instruction
manual), before it starts to dry.
In summary, all of the test methods are capable of measuring field den-
sity with reasonable accuracy and precision. The direct methods are straight-
forward, use rugged and inexpensive equipment, and take considerable time to
perform. The nuclear guage method uses expensive equipment (yet its purchase
price is less than the labor cost of one inspector/technician for one year),
requires constant attention to calibration and maintenance, and yields very
rapid nondestructive test results. Operator fatigue with the nuclear guage is
less than it is with the simpler methods. And with the nuclear guage the in-
spector is left with more time to observe construction operations and perform
other tests. Rapid results are particularly valuable during process control
tests of fill compaction, for they contribute significantly to lower construc-
tion costs.
Specific Gravity Test Method
The specific gravity of most soils tends to be fairly uniform in a
limited area because of the sorting of many geologic processes. This is
demonstrated in Table 3-1 where a coefficient of variation of one to four
percent has been reported.
Because of the relative uniformity of specific gravity, most tests to
define it in a soil mass are made during the site characterization. The
tests must be performed in a laboratory environment and can take one or more
hours to perform. Therefore, the performance of this test is suitable as an
occasional check on the consistency of earlier test values. It is, however,
of little concern or value for process control or acceptance testing.
Grain-Size Distribution Tests
These test methods use square screen openings to separate soils into
size fractions. Soils are generally classified as: (a) gravel, larger than
the No. 4 screen; (b) sand, between the No. 4 and No. 200 screens; and
(c) fines, smaller than the No. 200 screen (Dept. of the Army, 1970). The
distribution of particle sizes for gravel is of little concern at a disposal
facility, especially during construction. Sand sizes are fractionated on
square-opening screens ranging from four openings per inch (No. 4) to 200 open-
ings per inch (No. 200). Finer sizes are fractionated on the basis of the
rate of sedimentation of equivalent spherical particles in water, using Stokes'
Law to calculate the rates. None of the methods are rapid tests, and all
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require performance in a laboratory environment and the nearly constant atten-
tion of a test technician.
Sand samples must be thoroughly dried before they can be shaken through
a nest of sieves for the sieve analysis test. If the sand contains very few
fines, the entire test for a single test portion can be made in under an
hour, if hot air drying is used. The shaking through the screens, weighing
of individual fractions, and calculations can be performed by one man with a
mechanical shaker in under 30 minutes. Sampling time, travel time, and dry-
ing time are variables. Several samples can be prepared at the same time,
with the per test time thus reduced.
If the sand contains plastic fines, drying will cause the clay particles
to adhere to the fine sand sizes, giving erroneous test results. If a wet
test portion is weighed (a moisture sample tested for correction of the wet
sample to dry weight) then the wet sample can be washed through the No. 200
screen. The fine particles will pass and the coarse residue, when dried,
can be used for the sieve analysis test. The loss in weight is the fines
content. The fines are not normally retained. The test is time consuming
and requires constant attention from the operator. It also requires a
source of water and of drying heat. Two tests per hour would be a rapid
test rate; however, the results would not be available until the residue is
dried and sieved.
The standard hydrometer test requires extensive time and expertise for
sample preparation and for test performance. A vibration free test area,
glassware, and temperature controls are needed. The test requires several
hours to perform, including the time for soaking in the deflocculating
agent. This is the only exact method for determining the percent silt
sizes (0.074 mm to 0.002 mm) and the percent clay sizes (finer than
0.002 mm). Several samples can be tested simultaneously. This test may be
useful for acceptance testing but is not normally used for process control.
The pipette method and the decantation method (Mills, 1970) are varia-
tions on the standard hydrometer method. They are useful only to establish
total percent silt (0.074 mm to 0.002 mm) and total percent clay (finer than
0.002 mm). Stokes' Law can be used to determine the settling rate of clay
sizes. The soil samples are placed in a container of specified height and
deflocculated with standard dispersing agent for a period of one hour. The
soil-water mixture is agitated and then allowed to sit quietly for a speci-
fied time, usually a few minutes. This is the theoretical time for settle-
ment of all sand and silt sizes below a specified level. At that time, all
liquid with clay in suspension is removed by either a pipette or by decanta-
tion. This is repeated until the water is clear, after the settling time,
indicating that all clay sizes are gone. Then the residue is dried and
tested by sieving; the material passing the No. 200 screen is then all of
silt size. This form of sedimentation test for silt and clay sizes should,
when properly conducted, yield the same useful information as the more in-
volved hydrometer test, but with equipment better suited to field laboratory
use. Several samples can be tested at the same time; with total time per
sample of about two hours. Before use, the technique and equipment should be
calibrated against the standard hydrometer test to produce any systematic, or
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calibration, correction that may be needed. Thereafter, the suitability of
soils, specified to have a given clay content, can be easily verified.
Atterberg Limits Tests
The liquid and plastic limits, and the plasticity index, are used
primarily in the identification and classification of soils. They are not
fundamental parameters; rather, they are used only as indicators of potential
behavior. In association with clay content (finer than 0.002 mm), an activity
ratio can also be calculated, which is related to mineralogy, and thus also to
the potential for swell and shrinkage.
The numerical values for the Atterberg limits needed for the identifica-
tion of a sample according to soil type or group need not be exact. A five
or ten percent variation, or error, is often acceptable for soil classifica-
tion purposes. For most common clay minerals, the liquid limit is dependent
upon the types and amounts of clay minerals present. It may vary from 25 per-
cent water content to well over 100 percent. The plastic limit varies,
usually, over a very small range, about 15 to 30 percent water content; how-
ever, when particular clay minerals predominate, the plastic limit can vary
over a much wider range of water contents (Spigolon, 1956).
Except when the Atterberg limits are to be used in a well researched
empirical correlation with another soil parameter, a five to ten percent
error yields a reasonably correct identification and consistency within a
soil group. The one point liquid limit test will yield a liquid limit within
one or two percent error of the standard multipoint liquid limit. Consider-
ing the time savings realized, with little or no sacrifice in the value of the
test, the one point method is frequently used. In view of the limited experi-
mental data usually associated with most correlations, it is probably ac-
ceptable even in such applications. The Atterberg limits tests require up
to one hour to perform, not including the drying time needed to determine
moisture content. A competent technician can perform several tests concur-
rently, so that ten or twenty tests per day can be performed. These are
laboratory tests and are not amenable to field use. However, they can be
reasonably approximated by the visual-manual field expedient methods of ASTM
(1982) Designation D 2488-69, "Practice for Description of Soils
(Visual-Manual Procedure)".
Cohesive Soil Consistency Tests
Table 2-2 listed a relationship between unconfined compressive strength
and consistency; this is an attempt to quantify, by means of a test result,
a relative term. The standard unconfined compression test, ASTM (1982)
D 2166-66, "Tests for Unconfined Compressive Strength of Cohesive Soil",
requires either an undisturbed or a remolded sample, trimmed to a specified
size, and tested in a laboratory loading device at a constant loading rate.
The preparation, testing, and calculations for a sample can take well over
30 minutes of an operator's time. This does not include sampling and delivery
time. The procurement of an undisturbed sample can be time consuming.
A number of field expedient unconfined compression test devices are
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available. These usually include a small, simple device for securing a test
specimen from the surface area of a soil deposit. Or, they include a
portable, easily operated field testing machine for stressing the sample.
Most of these devices are useful and will yield an unconfined compressive
strength close to the laboratory derived value. Considering the broad
classifications of consistency, great precision cannot be justified. As it
is a process control test, rapidity and ease of testing are of utmost impor-
tance, and the field devices are thus qualified. For acceptance testing,
some reasonable precision is required. Since, as Harr (Table 3) has shown,
spatial variability of unconfined compressive strength is large compared to
the total variability, then a very precise test is unnecessary (see Equa-
tion 3-13 and the text immediately following).
The great imprecision of the field identification methods of Table 2
have lead to the development of testing devices which provide numerical values,
presumably independent of the technician's bias and capabilities. These in-
clude the Hand (Pocket) Penetrometer and the Torvane. Both are useful devices
for their intended purpose of aiding in establishing a consistency classifica-
tion. Their accuracy (systematic) error is questionable and their markings are
sufficiently spaced that precision is good on a general basis. If the devices
are viewed only as alternatives for a calibrated thumb they can be a
valuable site media verification or process control device. They should not
be relied upon for acceptance testing of unconfined compressive strength.
Water Content/Density/Compactive Effort Tests
Specifications for compaction control usually require that a soil be
compacted to a field density of a value at least equal to a predetermined
percentage of the density derived from a specified laboratory compaction test
method. Often, the water content of the soil at the time of compaction is
specified. This is done to achieve a soil structure (dispersed) which will
provide low permeability of the compacted soil at a disposal facility. Because
the test derived density is a function of the soil type in addition to the test
procedure, even slight variations in the soil composition can cause variations
in the density. Therefore, it is most desirable that every field density/
water content test for compaction control be compared to a laboratory
compaction test on the same soil. This is not always possible because of
the large number of field density tests necessary to evaluate a compacted
fill construction block and the relatively significant effort required for the
laboratory compaction tests.
In the early 1930's typical compacted fill specifications directed the
contractor to use specific equipment, specific soil from an approved borrow
area, a specific lift thickness, and a specific number of uniformly placed
passes of the roller (Johnson and Sallberg, 1960). It was recognized earlier
that, for a constant field compactive effort, there was a relationship between
field density and water content of the type shown in Figure 5, and that this
was used by engineers of the time in establishing the compaction criteria.
Proctor (1933), in his classic articles, advanced two ideas: (1) he
demonstrated the need for moisture control; and (2) he developed a laboratory
compaction test to establish the necessary water content. The soils of the
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southwestern U. S. tend to be naturally dry. When these are placed in a fill
at natural water content and compacted, the fill is usually very firm.
Proctor showed that a soil used in an earth dam, for example, and compacted
dry and hard would, upon wetting, become very soft. If it were placed
initially at the optimum water content, and if the strength were satisfac-
tory, then no further softening would occur upon wetting.
The moisture-density relationship at a specified, constant compactive
effort, was usually determined at the site by using a contractor placed
test section at various soil water contents. Then, the contractor would be .
required to use the same soil at the same compactive effort at the field
determined water content. Proctor set out to develop a laboratory test
that would duplicate the results of a field test section, obviating the
need for the costly field work. This would also permit re.testing for a
change in soil composition, but always at the same field compactive effort.
The test developed by Proctor (1933) was the basis for all present day
impact-compaction tests (Hveem, 1957). The original test resulted in the
present 25 blow Standard Proctor Compaction Test, ASTM (1982) Designation
D 698-78, "Moisture-Density Relations of Soils and Soil-Aggregate Mixtures".
That test, as described above, defines the "maximum" density and "optimum"
water content for a single laboratory compactive effort, and was originally
intended to duplicate the typically specified field compactive effort of the
early 1930's. It can be used to duplicate that effort for any cohesive or
granular soil, without the need for a field test section.
As a result of the usefulness of the laboratory test and its sensitivity
to soil composition change, there developed in the late 1930's, and through
the war years of the early 1940's, a tendency toward the end result compac-
tion specification commonly used today. Contractors were expected to compact
the soils to a high percentage of their maximum density, at or near the
optimum moisture content, as determined by the laboratory test. Compliance
was determined by a field density/moisture test. This type of end result
specification is extensively used today.
During the early 1940's, at a time of extensive airfield construction,
higher compactive efforts than ever before were used on base courses. The
standard Proctor [ASTM (1982) Designation D 698-78] test was no longer appli-
cable. Therefore, a modified Proctor test, at a higher laboratory compactive
effort was developed. This became the 25 blow Modified Proctor Compaction Test,
ASTM (1982) Designation D 1557-78, "Moisture-Density Relations of Soil and
Soil-Aggregate Mixtures".
In the 1950's there developed a confidence in compacted fills and these
were end result specified for highways, airfields, dams, and structural fill.
A wider variety of compaction equipment was developed. The prescription type
of specification gradually faded, largely as the result of legal problems re-
sulting from its use. The laboratory compaction tests became "index properties"
(Peck et al. 1974) sensitive to soil composition, but no longer were they
commonly used as a method to establish optimum moisture content.
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With the advent of specifications for light compaction of fill at
disposal facilities, using tractor treads for example, there has been an
attempt to devise laboratory compactive efforts to duplicate field compaction,
in the original Proctor manner. This has resulted in Nonstandardized Proctor
Compaction Tests in which the number of blows per layer, or even the number
of layers, is different from the ASTM standard methods.
Johnson and Sallberg (1962) discussed the various compaction tests that
are in use. Because there sometimes existed a discrepancy between the labora-
tory impact-compaction/water content/density curves and the field derived
curves, other forms of compaction, such as kneading, have been used in the
laboratory (Antrim, et al. 1970).
All of the impact and kneading compaction tests have limitations and re-
quire a laboratory environment. For low plasticity soils, a complete test can
be performed in one to two hours if a mechanized blender is available. Opera-
tor fatigue can be lessened by the use of a mechanical compactor. Drying of
samples for water content determination can take from a few minutes to over-
night, as discussed earlier in this report. If the soil is a medium to high
plasticity clay, then time delays may be needed to alter the water content of
the soil throughout the small lumps of soil prepared for testing. This time
will be a function of the permeability of the soil and its percent fines.
A very useful, but uncommonly used, apparatus and test method is the
Harvard Miniature Compaction Apparatus (Wilson, 1970). This is a kneading
type compactor using a small mold, about 1.31 inches diameter by about
2.82 inches high, suitable only for fine grained soils (soils for which half
the material will pass a No. 200 screen)= Because of this smaller apparatus
and the simplicity of its use, the method can be easily adapted to field labora-
tory operation, or even to field use at the compaction site. The number of
layers and number of tamps per layer can be varied as necessary, as with the
Proctor tests. Therefore, the Harvard Apparatus can be used to establish a
moisture-density curve comparable to that established by the larger equipment.
For both types of apparatus, the relationship between the field and the labora-
tory compactive effort must be established for the test to yield the optimum
moisture content. It is likely that the moisture-density curve from the
Harvard Apparatus kneading action will come closer to the field curve than the
moisture-density curve from the impact compaction test, because its kneading
action is closer to those actions actually accomplished by sheepsfoot and
rubber tired rollers. Furthermore, the apparatus yields a cylindrical
specimen, when extruded from the compaction mold, that is of the correct
dimensions for unconfined compressive strength testing. In summary, it is
the authors' opinion that the Harvard Apparatus test lacks only the mantle
of standardization to equal or exceed the usefulness of the more conventional
Proctor impact tests for fine grained soils.
The time consuming and tedious laboratory compaction test procedures do
not lend themselves to rapid or frequent testing. Theoretically, every field
density test should have an accompanying laboratory derived curve if the
specifications continue to be written on the basis of density. This has.
lead to the development of several quick methods, all based on the nest of
curves concept.
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The files of many agencies, such, as state Highway Departments, contain
thousands of curves of standard or modified Proctor compaction tests for a
variety of soils. Woods and Litehiser (1938) developed a family of curves
for Ohio soils, all of about the same shape, and varying in maximum density
and optimum moisture content. Similar nests of curves have been developed
by others, either on a regional basis or on a job site basis. The Ohio
Highway Department Method uses the result of a compaction test of the field
density soil, wetted to near optimum moisture content, and a nest of curves
of Proctor Needle Penetration resistance [Proctor, 1933; ASTM (1982) Designa-
tion 1558-71, "Test for Moisture-Penetration Resistance Relations of Fine-
Grained Soils"], to establish the "correct" moisture-density curve, from which
the maximum density and optimum moisture are read.
Variations on the nest of curves method involve the (a) One point
Compaction Method, and (b) the Two point Compaction Method. These are
described in detail in Appendix B of Engineer Manual EM 1110-2-1911 (Dept. of
the Army, 1977). In the one point method, the soil from the field density
test is allowed to dry to a water content below optimum. It is then com-
pacted using the laboratory procedure at the one water content. The water
content and density establish a single point in the nest of curves, from
which the estimated correct curve is developed by drawing it to the same
shape as the rest of the family, through the test point. The two point
method is similar except that two points are established. This is expected
to give a better estimated curve.
The nest of curves methods are only as good as the basic data. Where
the local soils have been well tested and the data are consistent, these
methods can give fairly reasonable estimates of the true moisture-density
curve. This is better than the common method of running one test curve for
a soil type and applying it to all soils on the site that can be matched to
it visually, for visual matches are often misleading.
Another rapid compaction test method is that of Hilf (1970), who developed
it for use on Bureau of Reclamation projects. In this method, the field mois-
ture is estimated to be on the dry side of optimum. A field sample is selected
and compacted at field moisture. Second and third samples are compacted at
two percent and four percent above the field moisture in order to bracket the
unknown optimum moisture content. A curve is fitted to these points and,
without the need to determine water content, the percentage of maximum density
and the difference of the fill soil from optimum moisture is established. This
method is useful only for low plasticity cohesive soils, liquid limit less than
50, so that the moisture additions will mix well with the soil. The total test
time is about one hour. This is a potentially useful method, especially when
compared with the more labor intensive, conventional five point laboratory
impact tests (Winterkorn and Fang, 1975).
Cohesionless Soil Relative Density Tests
Moist sands bulk, or become less dense, when poured or dumped, because
of a film of moisture about each, grain and the effect of surface tension.
Therefore, in the performance of maximum and minimum density tests, the sand
samples must first be thoroughly dried. This is cumbersome and time consuming
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because of the quantities involved. The maximum density test requires a
vibrating table; this is. not normally found at a field laboratory. Howevers
sand samples can be obtained from the source stockpiles and tested ahead of
time. Or, samples can easily be taken at the end of the day from the fill
and tested overnight, with results available within one hour or less after
the sand is dried.
The Modified Providence Vibrated Density Test is a field expedient test
for maximum density. It uses the blows of a hammer on the mold to cause
densifications rather than the more consistent densification caused by a
vibrating table. If performed properly, this procedure should be almost as
valid as the method requiring the use of a more expensive vibrating table.
Also, this method can save the time and effort of transporting samples to the
central laboratory.
It has been the experience of one of the authors (Spigolon) that process
control of sand densification can be made by the use of a penetrometer. On a
major fill project in Memphis, Tennessee, a dredged sand, with about 15 per-
cent content passing the No. 200 screen, was being vibration compacted to
75 percent relative density. A 5/8 inch pointed end steel rod was driven into
the fill by use of a 20 Ib hand-held drop hammer. This device was used to
prepare a hole in the soil for insertion of the radioactive source rod of a
nuclear moisture-density gage. The test technicians quickly became adept at
using dynamic penetration resistance (number of blows) of the hammer device
to tell if the fill sand had been adequately compacted before the density
test was made.
Soil Color Tests
Although not a formal index property, the color of a soil can often be
used to compare soils. Often, differences in mineral composition or even
oxidation (reduction) above or below the water table can be compared by the
color„ For greatest consistency among technicians, it is recommended that
standard Munsell color charts be provided for field use during the site inves-
tigation and also during site media verification.
Organic Content Tests
The organic content of some soils-is so great that they are unusable
for fill as a liner or as a cover. As a specification item, the organic
content can only be tested by elaborate chemical laboratory tests. Among
procedures for determining organic content are those of Schmidt (1970) and
Rankin (1970).
Permeability Tests
Specifications for compacted clay liners for disposal facilities often
require that samples be taken from the fill and laboratory tested for perme-
ability. A complete discussion of this topic is beyond the scope of this
report. The reader is referred to the papers by Olsen and Daniel (1981) and
an EPA report-in-progress by ABC Dirt, Inc. (1981). There is some concern
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that the action of securing the samples densities them and produces perme-
abilities as much as one or two orders of magnitude in error. The variation
of permeability over a site was discussed in the paper by Vieira, Nielsen,
and Biggar (1981) (see Section 6, Recommendations for Further Study).
Geomembrane Hydrostatic Leak Detection Test
There is one commonly used method for checking the impermeability/integrity
of an entire installed geomembrane which is very unlike the geomembrane/
geotextile tests and observations to be discussed. As will become evident,
this hydrostatic leak detection test does not involve a very formalized or
specific method. Thus it does not meet the definition of a test. However,
the method is also more than a mere observation. This is why the hydrostatic
leak detection test is presented here.
The hydrostatic leak detection test calls for the filling of an entire
geomembrane-lined excavation with water, so as to completely submerge the
geomembrane (or at least that major portion of it which will be lining the
waste), and, in effect, create a pond. Any leak in the geomembrane is then
detected by the presence of air bubbles. Pinhole size leaks can be detected
by causing air pressure beneath the geomembrane to encourage air bubbles.
This air pressure can be the result of so simple a procedure as having a man
walk over the geomembrane, particularly along the seams (likely locations for
leaks).
There are limitations to the hydrostatic leak detection test. The detec-
tion of a leak also means the seepage of water into the soil beneath the geo-
membrane. Also the pumping costs, both in and out of the excavation, are
considerable in terms of the time, equipment and labor required.
However, the hydrostatic leak detection test can provide great assurance
in the impermeability/integrity of an installed geomembrane. It would be a
particularly- desirable method for an inspection group which wanted great
assurance that an installed geomembrane for a surface impoundment had no
detectable leaks.
Geomembrane and Geotextile Seam Integrity Tests
Geomembranes and geotextiles receive expanded discussion in this report.
This subsection on geomembrane and geotextile seam integrity tests includes
discussions of general considerations, field test methods, observations and
off-site materials inspection.
A discussion of quality assurance field test methods and observations
for geomembranes and geotextiles used in a hazardous waste disposal facility
must begin with an explanation.
The techniques for the installation and use of these products (geomem-
branes and geotextiles) are still evolving. The development of a field test
method or observation to assure that a technique will work to its designed-
for performance standard occurs after the technique has been proven. And the
field test method or observation is developed to assure the performance of
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that specific technique. That the techniques are still evolving obviously
means that so are the quality assurance field test methods and observations
(Reference: verbal communication with Paul Miller, Vice Chairman, ASTM
Subcommittee D 18.19, "Geotextile Applications" and ASTM Subcommittee D 13,61,
"Geotextiles"). Thus any presentation of accepted and commonly used field
test methods and observations in this subsection must be in the context of
this evolutionary reality (see Section 6, Recommendations for Further Study).
The use of a geomembrane or geotextile in a hazardous waste disposal
facility requires that quality assurance be provided for both the workmanship
and the material. The quality assurance for the workmanship can be divided
into two aspects: (1) quality assurance of the workmanship involved in the
seam bonding, and (2) quality assurance of the workmanship involved in the
installation of the product. The quality assurance of the workmanship in-
volved in the seam bonding will be discussed in the subsection on Field
Test Methods. The quality assurance of the workmanship involved in the
installation of the product will be discussed in the subsection on Observations,
The quality assurance of the material will be discussed later in the subsec-
tion on Off-Site Materials Inspection.
Field test methods; The quality of the workmanship involved in seam
bonding can be assured by testing the seam's integrity after bonding.
Methods for testing the seam's strength include the bonded seam strength,
breaking strength and peel adhesion methods. Each of these methods provides
credible assurance of the seam's strength, but as they differ in the results
they provide no relative meriting of these methods will be attempted.
Methods for testing the seam for anomalies include the air lance, vacuum seam
and conductivity methods. The air lance is the most rapid of these methods
but also the least capable of locating all anomalies. By itself it does not
adequately assure seam integrity. The vacuum box and conductivity methods
both provide great degrees of confidence in the seam integrity. Each has its
relative merits and the preference of one over the other should be left to
the permittee's forces as a site-specific, usage-specific decision.
All three of the seam strength testing methods require the cutting of
bonded seam specimens. This is a destructive requirement causing the effort
involved in specimen replacement. An alternative is to bond a seam of greater
length than that required. Then the specimens can be secured from the excess
seam and these methods would then not be destructive in nature. However, this
alternative obviously also contravenes the random sampling concepts described
in Section 3. The decision to select this alternative is therefore left to
the permittee's forces, to be made on a site specific basis.
As is obvious, these methods test only the seam integrity. This limita-
tion is also addressed in Section 6, Recommendations for Further Study.
Observations: As has been stated before, the worth of the observations
in a quality assurance program for a hazardous waste disposal facility
depends more on the technical expertise and willingness of the quality
inspector than on specific details of observation technique. This is
certainly true for observations on the workmanship involved in the installa-
tion of a geomembrane or geotextile.
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The quality inspector should assure that the workmen are in fact install-
ing the product as per the design by some acceptable, and nondestructive (to
the product) technique.
The quality inspector should also conduct a one hundred percent inspec-
tion of the product after installation. During this inspection he should
look for anomalies. If the product installed is a geomembrane, anomalies he
should look for include pinholes, air bubbles beneath the membrane, inadequate
cover over the membrane particularly along the shoulders of a trench such
that the membrane would be exposed to direct sunlight, etc.
The most important consideration for a quality assurance program which
includes observations to assure the quality of workmanship involved in the
installation of a geomembrane or geotextile is the selection of the quality
inspector to make these observations. The inspector selected should be
competent, willing and expert in geomembrane-and geotextile installation.
This selection is critical to the effectiveness of the entire program.
Off-site materials inspection: When a geomembrane or geotextile is
included in the design of a hazardous waste disposal facility, the permittee
and his design group expect the product to perform to the specifications
provided by the manufacturer. But there is an inevitable degree of un-
certainty as to whether the product which actually arrives on site will in
fact perform to those specifications. This uncertainty results in part from
doubt that the product is, in fact, what it is supposed to be. This un-
certainty will exist in some small degree regardless of the credibility of
the manufacturer. The permittee and his design group simply have no long
term guarantee that the product will perform to the specifications provided
by the manufacturer.
Given the importance of protecting the human health and environment, and
given the considerable costs of remedial action, the permittee and his
quality assurance group will seek to dispel this uncertainty. The usual
means of doing so is to order the products to be brought on site in advance
and then rely on independent laboratory verification for their quality. This
independent laboratory verification is not geotechnical in nature, nor is it
within the scope of this report. Therefore it will only be stated that this
independent laboratory verification should be of such a nature that the
permittee can be given that commensurate measure of assurance (see Section 5,
The Nature of a Quality Assurance Program) that the product will perform to
the specifications provided by the manufacturer.
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SECTION 5
THE QUALITY ASSURANCE PROGRAM
The term "quality assurance", as discussed in Section 1 of this report,
includes all of those planned and systematic actions of the permittee neces-
sary to provide adequate confidence to the regulatory agency that the dis-
posal facility will perform satisfactorily in service. That iss it will
perform in accordance with the design, and the permit, requirements. A
quality assurance program, whether formal or informal, should be an integral
part of the permit requirements.
A large body of technical literature has been published on the subject
of Quality Assurance/Quality Control (QA/QC) programs. Nearly all of it
involves manufacturing processes, nuclear power plants, or highway construc-
tion. Formal QA/QC programs in manufacturing processes (Juran, 1962; Grant
and Leavenworth, 1972) and, later, in highway construction (Willenbrock,
1976; TRB, 1979) emphasize statistical quality control. Both industries
involve continuous, repetitive production of a single item or a single pro-
cess. A formal QA/QC organization, the use of control charts for process
control, and formal acceptance sampling plans are used. The construction of
nuclear power plants has followed the manufacturing industry lead in estab-
lishing formal QA/QC plans (Bohannon, 1978),
ELEMENTS OF"THE QUALITY ASSURANCE PROGRAM
A quality assurance program for a hazardous waste disposal facility
must account for all the considerations given. It must include (a) a well-
defined plan of action, and (b) a specific plan of documentation, including
directives for disposition of records. Regardless of the existence of any
watchdog organization, all of the QA programs should be planned and executed
as if a watchdog organization existed.
The Quality Assurance Plan of Action
The permittee should prepare a written plan of action for the implementa-
tion of construction quality assurance. Despite the relative small size of
some disposal facilities, the human health and environmental protection
features of such projects require greater than ordinary attention to assure
the regulatory agency (through its watchdog organization, if it exists) of
their quality.
The suggested plan given below is based upon the proven and effective
"Contractor Quality Control Plan" of ER 1180-1-6 (Dept. of the Army, 1978).
The permittee's quality assurance plan should include:
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a. The QA organization planned
b. Proposed methods of performing QA inspections, both for process
control and for acceptance sampling and testing; this will include
inspections of the subcontractors' work
c. Proposed methods for initiating the corrective action when the QA
inspection determines that a block of work is unacceptable
d. Area of responsibility and authority for each individual to be used
in the inspection group for QA
e. Name and qualifications of each individual assigned a QA inspection
function; method of establishing and verifying inspector qualifi-
cations to perform specific tests or tasks
fo How inspection will be performed: -
(1) By inspectors employed by the permittee with designation of
individuals with their qualifications and specific tests to be
performed
(2) By subcontract inspectors, approved by the regulatory agency
(3) Use of test methods, approved by the regulatory agency
(4) Location, availability, applicability, and calibration of test
facilities and equipment
g. Procedures for advance notice and coordination of special inspections
where required
h. Procedures for reviewing all shop drawings, samples, certificates or
other documents for compliance with permit requirements and for
certification of their acceptability- to the regulatory agency
i. Reporting procedures, providing for submittal and/or storage, at
specified intervals, and with proposed report format (see Quality
Assurance Documentation, later in this section)
j. A copy of a letter of direction to the permittee's inspection
representative, responsible for quality assurance, setting forth his
duties and responsibilities, and signed by a responsible official of
the permittee if not by the permittee himself
The regulatory agency, in reviewing the permittee's quality assurance
plan of action, should give particular attention to a plan for education of
workmen, construction management, and inspectors on the various quality
requirements of the disposal facility and the reasons for their existence.
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Quality Assurance Documentation
The ultimate objective of the project documentation is to provide a
permanent record of the permittee's self evaluation of his construction to
assure the regulatory agency that it was done in accordance with specification,
and permit, requirements. Because of the human health and environment
protection needs and because of the need for providing confidence to the
regulatory agency, the documentation must be complete.
Unless there is a specific permit directive for the amount and type of.
documentation, there will be the human tendency to reduce it to a minimum.
This will be especially true if there is no action taken with the documents,
i.e., review, audit, or submittal to a watchdog organization. The attitude
may well be, "If nobody is going to look at it and check it, why do a lot of
it?" Therefore, it is recommended that the following records be maintained;
a. Daily inspection reports; daily project diary kept by the senior
inspector at the facility
b. Data sheets; test and/or observations
Co Block evaluation reports
d. Design acceptance reports
e. Summary and checklist
Daily Inspection Reports
A daily summary report, a project diary, should be kept by the senior
inspector. This report provides the chronologic framework for identifying
and recording all other reports. At a minimum it should include the
following:
a. Date, project name, location, and other identification
b. Data on weather conditions
c. Unit processes, and locations, of construction underway during the
time frame of the report
d. Equipment and personnel being worked in each unit process, including
subcontractors
e. Descriptions of areas or units of work (blocks) being tested and/or
observed and documented
f. Off-site materials received, including quality verification
documentation
g. Calibrations, or recalibration, of test equipment, including actions
taken as result of recalibration
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h. Decisions made regarding acceptance of units of work (blocks), and/or
remedial action to be taken in instances of substandard quality
i. Signature by the permittee's senior person responsible for the
inspection program
Field/Laboratory Data Sheets
Original, handwritten data sheets should be maintained as part of the
project records. The requirements, and some example formats for data sheets,
for many of the necessary tests are given in Appendix B with each test
description. Because of their non-specific nature, no format can be given for
sheets to record observations. Recorded observations may take the form of
notes, charts, sketches, photographs, or any combination of these. For
identification, all data sheets should contain, as a minimum, the description
or title of the test or observation, the location of the test/observation,
type of test/observation, procedure used, personnel involved, results of the
test/observation, and comparison with specification requirements. Finally,
each data sheet should be signed by the senior member of the test/observa-
tion group involved.
Block Evaluation Reports
The design specifications delineate the quality characteristics which
must be inspected for each construction process. In each of these processes
the work is divided into blocks sized to accommodate the inspection program.
Therefore within each block there can be several quality characteristics
tested, each by different tests, each recorded on different data sheets.
These data sheets must be organized at the block level into a block evaluation
report. Each block must have its own separate block evaluation report. In
this way when the project or some well defined portion of the project ends,
the entire construction work can be summarized by a summary of all the block
evaluation reports. Also, given that the documentation is correct, the
quality of the entire project can be checked by comparing the design to a
summary of all the block evaluation reports.
Block evaluation reports should, at a minimum, include the following:
a. Description of block; use project coordinate system for areas and
appropriate identifiers for other units of materials or work
b. Quality characteristic being evaluated; reference to section of
specifications
c. Sampling method; how it was established
d. Sample increment locations; describe by coordinates or by a location
sketch on the reverse of the sheet
e. Tests or observations made; define procedure by name or other
identifier; attach data sheets; give number of sheets and
identify
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f. Summary of test data; tabulate data and give block average and block
standard deviation
g. Define acceptance criteria; compare sample data with requirements;
indicate compliance or non-compliance; in the event of non-compliance
indicate that the block was determined to be unacceptable and that
corrective action was initiated; in the event of non-compliance
and block non-acceptance, document the corrective action as per
a. through g.
h. Signature of senior member of inspection group involved
Design Acceptance Reports
All daily inspection reports, block evaluation reports, and field/
laboratory data sheets should be submitted to the permittee's design group for
evaluation and analysis for internal consistency and consistency with similar
previous work, i.e. acceptance. One of the objectives, and benefits, of
prompt evaluations is that errors, inconsistencies, anomalies, and other
problems can be detected and corrected as they occur, i.e. when corrective
action is easiest.
A periodic Design Acceptance Report should be prepared for project
records and for possible submission to a watchdog organization. The report
should accept the work and indicate that it complies with specification and
permit requirements. Each report may cover a time period, or a phase of
work, or a subsection of the total project, or the entirety of a unit process.
This report is also the periodic certification by the permittee of his
compliance with permit requirements.
Summary and Checklist
It may- be desirable, at the closure of any portion of a disposal facility,
or at the closure of the entire facility, to prepare a final summary report.
If the periodic block evaluation and design acceptance reports are complete
and voluminous, a final index or menu report will be helpful in showing the
content of all records and where they are located. This summary may be
coupled with any final certification required of the permittee. This summary
and checklist will be most important for the sake of quality assurance
documentation access and review.
Disposition of Records
Except for the handwritten field/laboratory data sheets, all other
reports are compatible to reporting and/or storage in either (a) photographic,
or (b) computer-compatible methods. It is expected that the original of all
reports, especially those containing signatures, will reside with the
permittee in a publicly acknowledged repository.
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The use of microfilm or microfiche provides a means of reporting that
requires very little storage space at the reported-to organization. This
method also allows recording of handwritten originals and of the inspectors'
signatures. By this method, information retrieval is accomplished by visual-
manual searches using a suitable microfilm reader machine.
Digital computer technology, including microcomputers, has progressed
such that even small engineering and business firms are using data base
management and data storage systems. Minimal paper and storage costs,
coupled with the speed and flexibility of data recovery and data transmission,
undoubtedly make computer-compatible methods desirable to use for hazardous
waste disposal facility documentation.
Although photographic and computer-compatible methods are presently
available, and may be efficient and cost effective, the relatively small
size of most disposal facilities means that conventional, paper-based,
methods will likely remain in use for the time being. Thus the use of
photocopy machines to make copies of reports for submittal to a review or
watchdog organization must be considered acceptable in spite of the signifi-
cant filing space requirements.
As a final documentation event, the permittee should require his design
group to update the facility design drawings at the closure of the facility.
These drawings should be equivalent to as built drawings, and with the
inspection summaries, will provide data in the event remedial action is
required in the future or in the event litigation, concerning the construction
and operation of the hazardous waste disposal facility, arises.
SUMMARY OF THE QUALITY ASSURANCE PROGRAM
The following flowchart, Figure 13, depicts the elements of the quality
assurance program which have been described in this section.
The EPA (Block 1), public (Block 2), and permittee (Block 3) arrive
at a level of quality (Block 4) for a given proposed hazardous waste disposal
facility. The permittee performs a site characterization (Block 5) for the
proposed facility. The level of quality arrived at and the site characteriza-
tion are used by the permittee to submit his permit (Block 6). The permit
includes,- amongst other information, design guidance and specifications
(Block 7) as well as the permittee's quality assurance plan of action
(Block 8).
The design guidance and specifications are used by those performing the
permittee's design function (Block 9) to produce the design (Block 10). (It
should be noted that this program is for the quality assurance of construction
and not the quality assurance of design.) The design is furnished to those
responsible for the permittee's construction and operations function
(Block 11). They use the design for all phases of their work: initial
construction, operation and closure. Their work is performed in blocks to
accommodate the quality assurance plan of action.
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EPA
1
PUBLIC
2
PERMITTEE
!
Figure 13. The Quality Assurance Program.
102
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Each block of work (Block 12) is observed and/or tested by those
responsible for the permittee's inspection function (Blocks 13, 14). These
inspectors are in constant communication with the construction personnel. The
two groups strive to catch and correct mistakes as these happen. The two
groups work synergistically to achieve the desired and specified level of
quality. The inspectors continually observe all construction and perform
tests and/or observations on finished blocks of work. In this way the
inspectors provide both process control and acceptance testing of the
construction.
Every observation and/or test is documented by a test data sheet
(Block 16). A copy of each test data sheet is furnished to the designers
(Feedback Block 9). Every block of work's inspection and acceptance or non-
acceptance is documented by a block evaluation report (Block 17). A copy of
each block evaluation repqrt is also furnished to the designers (Feedback
Block 9).
The inspectors determine if, during the construction of the block, any
information of design verification significance was learned (Block 18),
e.g. the exposure of site media contrary to that expected based on the site
characterization. If there is information of design verification signifi-
cance learned, they forward this information to the designers.
The inspectors also determine if the block of work is acceptable based
on the level of quality specified by the design (Block 19). If the block
of work is unacceptable the construction personnel will have to perform the
same work over, thus renewing the construction-inspection cycle. If the block
of work is acceptable the inspectors inform the construction personnel so that
they may continue their work (Feedback Block 11).
Off-site materials (Block 21) are also tested by the inspectors
(Blocks 13, 15). The inspectors prepare documentation for each test (Block
22) and each block of off-site materials (Block 23). Copies of both the test
data sheets and block evaluation reports thus prepared by the inspectors are
furnished to the designers (Feedback Block 9).
The inspectors determine if the off-site materials meet the level of
quality specified by the design (Block 24). If the materials are unacceptable,
the designers are so informed. The designers must then attempt to procure
off-site materials which do meet the level of quality specified by the design,
or they must make modifications to the design based on the quality of the
off-site materials on hand.
The inspection supervisor prepares a daily inspection report at the con-
clusion of the day's work (Block 25). A copy of this report is furnished to
the designers (Feedback Block 9).
The inspectors also prepare periodic design acceptance reports (Block 26).
These are furnished to the designers for their use in improving or verifying
the design.
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The inspectors complete their quality assurance documentation by the
preparation of a summary and checklist (Block 27) to index all of their
documentation. This summary and checklist is verified and signed by the
permittee (Block 28), who is ultimately responsible for the quality of the
facility.
The designers use the design acceptance reports and the other feedback
from the inspectors to prepare a final as built design (Block 29) of the
facility.
This as built design, along with all the other quality assurance docu-•
mentation (test data sheets, block evaluation reports, daily inspection
reports, design acceptance reports and the summary and checklist), is main-
tained for ease of access and review in suitable storage (Block 30).
Thus the program for the geotechnical quality assurance of the construc-
tion of a hazardous waste disposal facility is a closed loop, redundant
system. It is also a completely documented system which lends itself well to
the protection of human health and the environment.
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SECTION 6
SUMMARY
This section of the report summarizes the previous five sections and
presents recommendations for further study or investigation.
SUMMARY OF THE REPORT
The permittee of a hazardous waste disposal facility maintains a relation-
ship with the regulatory agency that is unique in the construction industry.
During construction, operation, and closure, the permittee is responsible for:
design verification, construction and operations, and quality assurance inspec-
tion. The regulatory agency derives confidence in the project quality from the
permittee's documentation of his work.
This report presents four major topics related to the permittee's responsi-
bilities during construction, operation, and closure of a hazardous waste dis-
posal facility:
a. The geotechnical parameters that should be tested and/or observed
and documented are identified and described.
b. The selection of sampling plans and sample sizes for the geo-
technical parameters are discussed within a statistical framework.
c. The commonly used laboratory and field testing and/or observation
techniques needed for the investigation of the geotechnical param-
eters are identified and described.
d. A quality assurance program suited to the unique responsibilities
of the permittee is presented and discussed.
The functions of the quality assurance inspection program during construc-
tion operations are (a) to evaluate the newly exposed site media, (b) to
evaluate the materials and workmanship of the construction group, and (c) to
assist the construction group in its process control.
The geotechnical parameters that should be tested during construction of
a disposal site include the soil index properties. These are the water content,
unit weight, specific gravity, grain-size distribution, Atterberg limits,
consistency, and laboratory compaction tests. Given these values, several
other index properties may be calculated; these include void ratio, porosity,
degree of saturation, plasticity index, and classification by an acceptable
105
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soil classification system. The soil index properties are good indicators of
the soil engineering properties used in design. Observations are made and
recorded on those aspects of construction not amenable to formal testing.
The selection of sample locations should be made on a random basis:
either a true random sample per construction block, or a systematic sample
with a random start. Sample size is independent of block size; it is a
function only of confidence level, maximum expected error, and block standard
deviation. The statistical methods presented are recommended because they
avoid the risks of relying on human judgement with its potential for bias or-
error. Conclusions derived by statistical methods are conducive to review.
All of the soil index properties identified are evaluated using standard
test methods. Most of these standard test methods are not commonly used be-
cause of time or equipment requirements. Acceptable alternative methods are
commonly used. This report contains a discussion of the merits and limitations
of the various test methods. Although certain test methods may have time or
cost advantages over others, no commonly used test method can be considered
totally superior to the others for the same index property. Hence none are
excluded from consideration for use.
In establishing a quality assurance (QA) program, the permittee should
consider the effect of several factors that arise because of his unique
construction related responsibilities. These include the workman, management,
and inspector identification with quality; the quality assurance system; the
nature and cost of a quality assurance program; the human factor; and the
problem of scale. The rationale for a watchdog organization is presented.
The recommended quality assurance program includes a detailed plan of
action and a documentation program. The project records should include daily
inspection reports, test/observation data sheets, block evaluation reports,
design acceptance reports, and a project summary. The documentation is
intended to provide the necessary confidence to the regulatory agency in the
quality of the facility.
RECOMMENDATIONS FOR FURTHER STUDY
This report has resulted from a study of the technical literature, visits
to hazardous waste disposal facilities, the personal geotechnical experiences
of the authors and their colleagues, and the extensive, collective, construc-
tion experiences of the U. S. Army Corps of Engineers. As a result of this
study, several gaps in knowledge have been identified. The following recommen-
dations are considered most useful for further study to support work related
to hazardous waste disposal facilities.
Quality Assurance Specifications
The use of statistically derived acceptance sampling and testing, as
discussed in Section 3, requires that the project specifications (a) use
performance oriented acceptance criteria, and (b) establish quality require-
ments in terms of both mean and variability (standard deviation) (Willenbrock,
1976).
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All naturally occurring soil deposits (the site media) and all construc-
tion processes have material variability. This natural variability must be
known to the designer so that it may be incorporated in the specified quality
acceptance requirements. Some of the published sources of such data were
presented in Section 3.
It is recommended that an extensive literature review be made to record
and summarize as many sources of measured natural variability as possible.
This is a continuation of the "sigma bank" concept of the Federal Highway
Administration. This work, naturally, should concentrate only on those
materials and processes used in the construction of a disposal facility. .
Permeability of Compacted Soil Layers
The authors are unaware of any published studies of the natural variabil-
ity of the permeability of layers of compacted soil. Yet, this variability
must be considered in establishing quality level requirements in the design
for compacted clay liners as discussed above.
After a diligent search of literature and unpublished data in various
public agency files, one or more field test sections of compacted soil should
be tested for permeability in a statistically developed experimental design.
Its purpose should be to establish the expected natural variability.
Rapid Compaction Control Test
Hazardous waste disposal facilities share a problem with all other com-
pacted earthfill projects. Because the maximum density and optimum mositure
content are sensitive to variations in soil composition, every field density
should be compared with a laboratory compaction test curve developed from the
same soil. However, the time and effort involved are usually prohibitive.
The permeability of a compacted clay liner depends heavily on the soil being
placed at or above optimum moisture content, making the determination of that
value more important than it is in conventional earthfill work. Thus the need
exists for more study of a rapid method for field control of compaction. A
combination of the Hilf rapid method and the Harvard Miniature Apparatus may
allow such rapid testing in the field, especially if some rapid moisture
method (e.g. the Speedy device) is used.
Geomembranes and Geotextiles
Designs for hazardous waste disposal facilities can call for the use of
geomembranes and geotextiles to achieve waste containment, slope stability,
trench cap integrity, etc. But the permittee needs assurance that the geo-
membranes and geotextiles used will perform to their designed-for standard.
As discussed in Section 4, the permittee's quality assurance for these
products usually results from independent laboratory verification of the
products (off-site materials inspection) and observations and tests of product
installation and seam bonding (workmanship inspection). The accepted test
methods for the products (those that lend themselves to a quality assurance
program for the construction of a hazardous waste disposal facility, as
107
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addressed in Section 4 and described in Appendix B) only test the membrane's
or textiles's seam integrity. With the exception of a hydrostatic leak detec-
tion test, there exist no accepted and commonly used tests for the entire in-
stalled product's integrity which also lend themselves to a quality assurance
program for the construction of a hazardous waste disposal facility. This is
especially significant given the unsubstantial performance history of these
products.
Additional field data and analysis are needed on the performance of geo-
membranes and geotextiles used in hazardous waste disposal facilities and
similar projects. Additional investigation of field test methods of these
products for quality assurance is also needed.
Verification of Off-Site Materials: Geomembranes and Geotextiles
As discussed in Section 4, the permittee usually relies on independent
laboratory verification for the quality of ge'omembranes and geotextiles brought
on site. The cost of such a quality assurance measure can be prohibitive,
both in terms of time and money. But given the uncertainty that exists, and
given the importance of protecting the human health and environment, the
permittee has little alternative.
There does exist a possible answer to this dilemna. The idea of a seal
of approval, an independent and credible verification of the membrane's or
textile's quality, is attractive and has precedent. Such a seal would assure
the permittee of the quality of the product and thus eliminate the prohibitive
cost of independent laboratory verification. This idea should be given further
consideration.
Geochemistry
As discussed in Section 1, geochemical considerations are beyond the
scope of this' report. However, this is an area where further study is recom-
mended. This further study should, among other objectives, answer the follow-
ing questions: What effects will the chemicals in hazardous waste disposal
facilities have on the liners (both soil liners and synthetic liners)? What
quality assurance procedures are necessary and sufficient to address the
geochemistry of a hazardous waste disposal facility?
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APPENDIX A
GLOSSARY OF TERMS
acceptance sampling and testing: The sampling and testing/observation of a
block of material or workmanship for comparison with specified require-
ments, resulting in acceptance or rejection of the block.
acceptance sampling plans The specified procedure for performing an accep-
tance sampling and testing for a given quality characteristic, including
block size, number and location of samples, and acceptance criteria.
accuracy: The closeness of agreement of individual measurements or the
average of a large number of measurements with a "true" or accepted
reference value.
assignable cause: A factor, usually due to material or process change,
which contributes to variation in a systematic, or constant, manner and
which can be identified.
average? The arithmetic mean value; the summation of the individual values
divided by the number of individual values.
batch: A discrete unit or subdivision of a block of material within which
all var-iation is assumed to be random, such as a stockpile of sand,
a shipment of geomembrane, or a truckload of portland cement. See also
Sample Unit.
bias error: A constant error, in one direction, which causes the average of
a number of measurements to be offset from the true or accepted reference
value. See also Accuracy, Systematic Error.
block: An isolated quantity of material from a single source. A discrete
quantity of material that is presented for inspection and acceptance.
A measured amount of construction assumed to be produced by the same
process.
block-by-block sampling and inspection: The sampling and testing/observation
of successive construction blocks for process control or acceptance
evaluation.
characteristic: A measurable property of a material, product, or type of
construction. See also Quality Characteristic.
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coefficient of variation: A measure of variability; the standard deviation
of a set of values expressed as a percent of the average, or mean, of the
values.
confidence interval: The range of values that has a designated degree of
assurance, or confidence level, of including the true value upon repeated
sampling. See also Maximum Error.
confidence level: The probability that a confidence interval includes the
true value.
confidence limits: The maximum and minimum values which define the confidence
interval.
construction: The end result of processing and placing materials or products
in accordance with explicitly stated conditions.
construction block: A measured amount of construction assumed to be produced
by the same process. See also Block.
control of quality: Measurements of construction quality characteristics
which are significant for controlling the construction materials and/or
workmanship to meet specification requirements, combined with a system
for initiating corrective action when off-standard quality is encountered.
See also Process Control, Quality Control.
defect: A failure to comply with specified quality requirements for visual,
dimensional, or physical characteristics.
duplicate samples: Two samples collected from the same block, or population.
error: The numerical difference between the measured value of a quality
characteristic and its mean, true, or reference value.
fat clays: These are high plasticity clays, i.e. those having a liquid limit
greater than 50. These clays are classified as CH in the Unified Soil
Classification System.
geomembrane: A thin, flexible, impervious layer or sheet of plastic or rubber
that is commonly used in geotechnical engineering. Geomembranes are used
to prevent the migration of groundwater. They are also in strengthening
applications similar to those for which geotextiles are used. Among the
most widely used geomembranes are the high density polyethylenes (HDPEs).
geotechnical engineering: That part of science (and art) in which one applies
the laws of mechanics and hydraulics to solve engineering problems
associated with soils.
geotechnical parameters: These are quantities, derived from tests and/or
observations, which are conveniently used for indirectly measuring an
engineering property of soil or rock. See also Soil Index Properties
Tests.
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geotextile: A synthetic material in the form of cloth or mesh that is commonly
used in geotechnical engineering. Geotextiles are used in the construc-
tion of pavements, earthworks and French drains. Geotextiles are also
used to strengthen railroad beds and to control erosion. Among the most
widely used geotextiles are the polyester fabrics.
homogeneous: Of the same nature or kind throughout; the state of being
perfectly blended; zero degree of segregation.
imprecision; The degree of lack of precision; usually characterized by the
standard deviation, or the coefficient of variation, of the errors of
measurement. See also Precision, Standard Deviation.
increment: The portion of material removed from a sample unit (part of a
block) during sampling. See also Sample Increment.
inspection: The process of measuring, examining, testing, gauging, or
otherwise comparing a block of construction with the applicable
requirements.
lean clays: These are low plasticity clays, i.e. those having a liquid limit
less than 50. These clays are classified CL in the Unified Soil
Classification System.
material: A part, component, or ingredient which, when combined with other
materials, forms a product.
material quality: The quality of a material or product which is the combined
effect of composition and placement process.
maximum error: The greatest difference between the estimate made from a
sample and the true or reference value that may occur with a designated
degree-of assurance (confidence level). See also Confidence Interval.
mean: The arithmetic average; the sum of a number of individual values
divided by the total number of values.
natural process tolerance: The actual capability limits of a construction
process applied to a specific material; the limits within which all but
a specified fraction of all measured values of a material quality
characteristic will fall.
natural variability: The variability of any specific material quality charac-
teristic measurement data resulting from natrual random variation in
composition and/or placement processing.
nonrandom error: Difference between a measured value and its true value due
to a significant, consistent, assignable cause.
observation: An act of recognizing and noting some fact or occurrence. The
act of seeing or fixing the mind on something.
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one hundred percent inspection: Inspection of each and every unit of material
or work in a construction block; screening.
parameter: A quantity conveniently used for indirectly measuring a variable
property of a material or any other statistical population.
permittee: The-holder of a permit to construct and operate a hazardous waste
disposal facility, i.e., the owner or operator.
population: The total set of possible measurements of any quality charac-
teristic. See also Universe.
precision: The degree of mutual agreement among individual measurements of a
consistent material made under prescribed, like conditions.
process control: A procedure whereby construction equipment, processes, and
operations are continually inspected to yield a product conforming with
project specifications, together with procedures for correcting
unacceptable materials or work. See also Quality Control, Control of
Quality.
profile: The vertical arrangement of soil layers.
quality: The level of performance of a product, a construction process, or
a construction block, measured in terms of specified requirements.
quality assurance: The planned and systematic actions necessary to provide
adequate confidence that a structure or a system will perform
satisfactorily in service, i.e., in accordance with design requirements.
quality characteristic: A physical or chemical property or any other require-
ment used to define the nature of a product or process.
quality control: See Control of Quality; Process Control.
quality personnel management: The implementation of management practices to
effect worker involvement in quality assurance.
random error: A difference between a measured value and the true value that
appears to occur without aim, reason, or cause, depending only on chance.
random sample: A sample in which each of the sample units has been selected
at random from the construction block.
repeatability, reproducibility: A special purpose designation of precision
for particular operations that require specific definitions for each
use. Repeatability is customarily used to designate precision for
measurements made within a very restricted set of conditions (for example,
individual operators), while reproducibility is customarily used to
designate precision for measurements involving variation between certain
sets (for example, laboratories) as well as within them. (ASTM Designa-
tion E 456-72).
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replicate samples: A series of more than two samples taken from the same
block,
representative sample: A sample without bias; a true sample; a sample whose
quality is the "average" of the block.
sample: A collection of units of increments, usually chosen at random from
a construction material, a construction process block, or an incoming
shipment, to represent the whole,
sample increment: The portion of material removed (or tested in place) from
a sample unit selected at random from a block during sampling. See also
Increment.
sample unit: A small part of a construction block. It is assumed that
variations within the unit are random, i.e., due to chance.
screening: See One Hundred Percent Inspection.
soil index properties tests: These are physical tests of soils yielding
numerical results known as index properties.
specification: The detailed quality characteristics which a material or
process is required to fulfill.
standard deviation: A measure of variability of data about the average, or
mean, value; the square root of the mean of the sum of the squares of the
individual deviation from the mean.
stratified random sample: A random sample in which increments are taken at
random from each of the several strata, or sub-blocks, of the larger
block, or population.
systematic error: A constant error, in one direction, which causes the
average of a number of measurements to be offset from the true or
reference value; see also Accuracy, Bias Error.
systematic sampling with random start: A random sample in which the first
sample unit is chosen at random and successive units are selected
at uniform intervals of time, distance, area, or volume.
test: An act or process that reveals inherent qualities; usually involving
a specific and consistent technique and often a specific piece of test
equipment.
test portion: The part of a sample actually tested; usually obtained by
reduction of sample increments by random methods.
turnkey contractor: An individual or organization that contracts with an
owner to design, construct, and, usually, initially operate a facility.
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uniform random sample: A random sample in which every sample unit within the
block, or population, has an equal chance of being selected.
universe: The total set of possible measurements of any quality characteristic.
See also Population.
variance: The square of the standard deviation; a measure of variability of
data about the mean, or average; the mean of the sum of the squares of
the individual deviations from the mean.
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APPENDIX B
TEST METHOD DESCRIPTIONS
The descriptions presented in Appendix B are only intended to give the
reader general information about the specific test methods. More detailed
information can be obtained from the references noted for the various test
methods. Data sheets for some of the test methods are provided as illustra-
tive examples. These data sheets are merely examples and their inclusion
here does not connote that the authors recommend that they specifically be
used.
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APPENDIX B
Method Number'
Parameter Measured: Water Content
Standard Oven-Dry 1
Standard Nuclear Moisture/Density Gage 2
Gas Burner - 3
Alcohol Burning 4
Calcium Carbide (Speedy) 5
Microwave Oven 6
Infrared Oven 7
Parameter Measured: Unit Weight
Standard Laboratory Volumetric 8
Standard Laboratory Displacement 9
Standard Field Sand-Cone 10
Standard Field Rubber Balloon 11
Standard Field Drive-Cylinder 12
Standard Nuclear Moisture/Density Gage 13
Parameter Measured: Specific Gravity
Standard Laboratory 14
Parameter Measured: Grain-Size Distribution
Standard Sieve Analysis (+200 Fraction) 15
Amount of Soil Finer than No. 200 Screen (Wash) Standard 16
Standard Laboratory Hydrometer (-200 Fraction) 17
Pipette Method for Silt and Clay Fraction 18
Decantation Method for Silt and Clay Fraction 19
Parameter Measured: Liquid Limit
Standard Multipoint 20
Standard One Point 21
Parameter Measured: Plastic Limit
Standard Laboratory 22
Parameter Measured: Cohesive Soil Consistency
Standard Unconfined Compression 23
123
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Method Number
Field Expedient Unconfined Compression 24
Hand Penetrometer 25
Handheld Torvane 26
Parameter Measured: Water Content/Density/Compactive Effort
25 Blow Standard Proctor Compaction 27
25 Blow Modified Proctor Compaction 28
Nonstandardized Proctor Compaction -29
Rapid, One Point Proctor Compaction 30
Rapid, Two Point Proctor Compaction 31
Hilf's Rapid 32
Ohio Highway Department Nest of Curves 33
Harvard Minature Compaction 34
Parameter Measured: Cohesionless Soil Relative Density
Standard Laboratory Maximum Density 35
Standard Laboratory Minimum Density 36
Modified Providence 37
Parameter Measured: Geomembrane/Geotextile Seam Integrity
Bonded Seam Strength 38
Breaking Strength 39
Peel Adhesion 40
Air Lance 41
Vacuum Box 42
Conductivity . 43
124
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Method No. 1
Parameter Measured: Water Content
Title of Test Method: Standard Oven-Dry
Principle of Test Method: This method determines the water content of a soil
sample by first weighing it wet and then again after it has been dried in
an oven.
Test Method
(1) Apparatus: Drying oven (thermostatically controlled, preferably
of the force-draft type), balance sensitive to 0.01 g., specimen containers
(tares) with lids, and a desiccator.
(2) Procedure: The procedure for this method consists simply of taking
a specimen of known weight$ placing it into an oven and drying it at a partic-
ular temperature and specified time. Upon drying the specimen is removed,
reweighed and the moisture content is calculated.
(3) Reference: ASTM D 2216.
Limitations: With many soils, close control of water content during field
compaction is necessary to develop a required density, strength and hydraulic
conductivity in the soil mass. Oven-drying is the standard test for deter-
mining water content of soils in the geotechnical engineering practice.
However, the method does not lend itself easily to field use. Although
temperature controlled ovens are currently available on some construction
sites, they require 4 to 12 hours for drying which may be excessive for the
close control of field compaction. All soils can be tested for moisture
content by ov.en-drying.
Status of the Method: Oven-drying of soil is the accepted laboratory method
among the geotechnical engineering profession for determination of water
content.
Calibration Procedure: N/A
Documentation of Test: Items to be recorded include the wet weight and the
dry weight. An example data sheet is provided.
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Method No. 2
Parameter Measured: Water Content
Title of Test Method: Standard Nuclear Moisture/Density Gage
Principle of Test Method: This method measures in place water content by
directing fast neutrons of known intensity into the soil and measuring the
intensity of slow or moderated neutrons reflected back.
Test Method
(1) Apparatus: Fast neutron source, slow neutron detector (readout
device and housing) and reference standard and site preparation device.
(2) Procedure: This method allows the determination of water content of
soil and soil aggregate in place through the use of nuclear equipment. The
equipment is calibrated to determine water content, as weight of water per
unit volume of material. Water content as normally used is defined as the
ratio, expressed as a percentage, of the weight of water in a given soil mass
to the weight of solid particles. It is determined with this procedure by
dividing the water content by the dry unit weight of the soil. Therefore,
computation of water content using the nuclear equipment also requires the
determination of the dry unit weight of the material being tested. Most
available nuclear equipment has the provision for measuring both the water
content and the wet unit weight. The difference between these two measurements
gives the dry unit weight.
(3) Reference: ASTM D 3017=
Limitations? The method described is useful as a rapid, nondestructive
technique for the in-place determination of the water content of soil. The
fundamental" assumptions inherent in the method are that the hydrogen present
is in the form of water as defined by ASTM D 2216, and that the material
under test is homogeneous. Test results may be affected by chemical composi-
tion, sample heterogeneity, and, to a lesser degree, material density and the
surface texture of the material being tested. The technique also exhibits
spatial bias in that the apparatus is more sensitive to certain regions of
the material under test. The nuclear method, which is applicable to a wide
range of soils, requires operation by an experienced technician in order to
obtain reliable measurements. A weakness in the nuclear method is that a
sample is not taken to determine the water content, and thus the test results
cannot be compared to the other water content methods, e.g. the oven-dry method.
In addition, this method requires equipment that utilizes radioactive materials
which themselves may be hazardous to the health of the operator. Effective
operator instructions together with routine safety procedures are essential
to the proper operation of this type of equipment.
Status of the Method: Nuclear gages offer a rapid and accurate means for
obtaining water content values for a wide variety of soils. Recent advances in
the design of nuclear equipment and a better understanding of the nuclear
principles involved have led to increasingly widespread use of nuclear gages in
earthwork construction control.
127
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Calibration Procedure: The apparatus must be calibrated against a reliable
direct method (e.g. oven-drying).
Documentation of Test: Items to be recorded include the water content and the
wet unit weight. An example data sheet is provided.
128
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DATA SHEET FOR FIELD DENSITY TEST
1 ' NUCLEAR GAUGE METHOD
\
A Moisture Standard Count
Sauge Type Serial Mo.
Bj Density Standard Count
FOR
JOB «303 NO.
SGURCfc OS- nflT.
MATERIAL DATE
TEST LOCATION
ELEVATION
TEST NUMBER
C Moisture Count
D Moisture Count Ratio
E Density Count
F j Air-Gap Count (if used)
6 | Density Count Ratio
H JBensfty, Wet Wtes"PCF
I j Moisture Content, PCF
J I Density, Dry Ht. , PCF
K | MOISTURE CONTENT, PERCENT
!
L 1 OPTIMUM MOISTURE, PERCENT
1
H ! DENSITY, DRY WT., PCF
N THEORETICAL DENSITY, PCF
0 PERCENT COMPACTION
P REQUIRED PERCENT COMPAC.
Q MQOE & PROBE DEPTH, IN.
R TYPE OF MATERIAL '
\/
/ \
/ \
C
A"
E • I
f or F
From S
4 Chart
From 0
& Chart
H - I
I
J
See Curve
From J
See Curve
£x 100
See Specs.
Laboratory No. /«tf
a'
t
f
,
Technician(s)
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Method No. 3
Parameter Measured: Water Content
Title of Test Method: Gas Burner
Principle of Test Method: This method determines the water content of a soil
sample by first weighing it wet and then again after it has been dried.
Test Method
(1) Apparatus: Gas stove, frying pan, balance and stirring rods.
(2) Procedure: This method determines the approximate water content of
soils by means of a gas-burner stove. The gas burner method involves the
weighing of a moist sample, placing the sample in a pan on the stove and
drying it to a constant weight, with occasional stirring of the sample to
prevent burning. The dry sample, first permitted to cool, is then reweighed
and the water content is determined.
(3) Reference: N/A
Limitations: The gas-burner method is used extensively for testing gravelly
material. Two or more samples may be tested concurrently. When care is
exercised to prevent overheating or burning of the sample, the testing time is
usually about 1/2 hour. The method is inaccurate for organic soils or for
those soils containing particles with loosely bound water, unless the drying
time is accomplished at a temperature of not more than 140°F (60°C) for 1 hour
or longer.
Status of the Method: The gas-burner method is used extensively as a rapid
method for testing gravelly soils in the field control of earthwork.
Calibration Procedure: N/A
Documentation of Test: Items to be recorded include the wet weight and the dry
weight. No example data sheet is provided.
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Method No. 4
Parameter Measured: Water Content
Title of Test Method: Alcohol Burning
Principle of Test Method: This method determines the water content of a soil
sample by first weighing it wet and then again after it has been dried by
alcohol burning.
Test Method
(1) Apparatus: Metal pan, balance, denatured alcohol and stirring rods,,
(2) Procedure: This method determines the approximate water content of
soil by burning alcohol that has been added to the soil. The general procedure
consists of placing a weighted quantity of moist soil in a pan, adding alcohol
to it and stirring the mixture, then igniting the alcohol. After ignition and
the complete removal of the moisture by burning, the sample is reweighed and
its water content is calculated.
(3) Reference: N/A
Limitations: The alcohol burning test is a rapid inexpensive method for deter-
mining the water content of soils. The method is usable with non-cohesive and
cohesive soils. The method should not be used if the soil contains a large
proportion of clay, gypsum, calcareous matter or organic matter. A large
quantity of alcohol is required for testing coarse gravelly material. For
multiple burnings, the testing time can be in excess of 1/2 hour. In terms of
safety, the alcohol burning test possesses the potential for fire. Care should
be exercised not to have alcohol on hand or in an open storage container near the
testing apparatus during the ignition phase of the test. The alcohol should be
stored in a "safety container*
Status of the Method: The alcohol burning method of obtaining the water content
of soil in the field has provided satisfactory results. Its use in the field
has been well established.
Calibration Procedure: N/A
Documentation of Test: Items to be recorded include the wet weight and the
dry weight. No example data sheet is provided.
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Method No. 5
Parameter measured: Water Content
Title of Test Method: Calcium Carbide (Speedy)
Principle of Test Method: This method determines the water content of a soil
sample by measuring the pressure developed when measured quantities of the
soil sample and powdered calcium carbide are mixed.
Test Method
(1) Apparatus: Calcium carbide pressure moisture tester, tared scale,
two each 1-1/4 in. steel balls, brush, cloth and scoop.
(2) Procedure: The calcium carbide gas pressure method for determining
water content consists of mixing measured quantities of moist soil and powdered
calcium carbide in a closed chamber and measuring the pressure developed by
the formation of acetylene gas. The reaction of calcium carbide and water
forms acetylene gas and calcium hydroxide. The pressure developed is
directly related to the amount of water entering into the reaction.
(3) Reference: AASHTO T 217.
Limitations: Only two sizes of testers are commercially available to test
for water content using this method: (1) 26 gram capacity model and (2) a
six-gram capacity model. The small chamber capacities of these devices
control the soil sample size to be used. As a result, this method is unsuit-
able for representative samples of coarse granular material. AASHTO T 217
recommends that this method should not be used on granular material having
particles large enough to affect the accuracy of the test (i.e. a soil with a
grain-size distribution such that an appreciable amount would be retained on
4.75 mm sieves). If a six-gram sample is used (according to AASHTO T 217),
the sample should not contain any particles that will be retained on the
2.00 mm sieve. The testing of heavy clays with this method requires special
handling.
Status of the Method: The apparatus for this method is relatively inexpen-
sive and well adapted to field testing. Use In the United States is extensive.
In the field the calcium carbide method has been used extensively in the
control of embankment construction. Normal testing time is less than 10 min.
A moderate amount of operator training is required. The calcium carbide
method is a standard method for rapid water content determination referenced
under AASHTO.
Calibration Procedure: A calibration curve is required.
Documentation of Test: Items to be recorded include soil sample weight,
powdered calcium carbide weight and the resultant gas pressure. No example
data sheet is provided.
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Method No. 6
Parameter Measured: Water Content
Title of Test Method: Microwave Oven
Principle of Test Method: This method determines the water content of a soil
by first weighing it wet and then again after it has been dried in the oven.
Test Method
(1) Apparatus: Microwave oven suitable for dryings balance, specimen
containers.
(2) Procedure: The procedure for this method is the same as that for
the Standard Oven-Dry method. That is, a specimen is placed wet onto a
balance and weighed. It is then placed in a microwave oven and dried
completely. It is then weighed again. The weight difference was the water
content.
(3) Reference: N/A
Limitations: Microwave ovens are not noted for their drying ability. There
are necessary safety precautions when using a microwave oven.
Status of the Method: This method is not commonly used. Although a microwave
oven heats much more rapidly than a conventional oven, it is an erratic dryer
at best. Thus this method should probably only be used to determine water
contents for soils which can be expected to have a low value, i.e. relatively
low water content.
Calibration Procedure: N/A
Documentation of Test: Items to be recorded include the wet weight and the
dry weight. No example data sheet is provided.
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Method No. 7
Parameter Measured: Water Content
Title of Test Method: Infrared Oven
Principle of Test Method: This method determines the water content of a soil
by first weighing it wet and then again after it has been dried in the oven.
Test Method
(1) Apparatus: Infrared oven suitable for drying, balance, specimen
containers.
(2) Procedure: The procedure for this method is the same as that for
the Standard Oven-Dry method. That is, a specimen is placed wet onto a
balance and weighed. It is then placed in an infrared oven and dried
completely. It is then weighed again. The weight difference was the water
content.
(3) Reference: N/A
Limitations: There are necessary safety precautions when using an infrared
oven. Infrared ovens are generally not widely available.
Status of the Method: This method is not commonly used. It can yield rapid
results, however. The method should be desirable to a large operation where
the benefits of rapid results outweigh the costs of the limitations above and
the initial investment.
Calibration Procedure: N/A
Documentation of Test: Items to be recorded include the wet weight and the
dry weight. No example data sheet is provided.
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Method No. 8
Parameter Measured: Unit Weight
Title of Test Method: Standard Laboratory Volumetric
Principle of Test Method: This method determines the unit weight of an
undisturbed soil sample by measuring its weight and volume.
Test Method
(1) Apparatus: Sampling tools, balance, water bath, volume measuring
device, oven and coating material (e.g. paraffin).
(2) Procedure: This method determines the density of cohesive soil in
its natural state, compacted cohesive soil, and stabilized soil by measuring
the weight and volume of undisturbed samples. The method briefly consists of
cutting out a block of soil, coating it with a known amount of paraffin,
weighing to obtain the net weight of the sample and immersing it in an over-
flow volumeter to determine the net volume of the sample, then dividing
through for the unit weight.
(3) Reference: AASHTO T 233.
Limitations: The method is suitable for any material that remains intact
during sampling. This metod is particularly adaptable to irregularly shaped
specimens and soil containing gravel shells, etc. Sample size is not limited;
large samples with coarse aggregate can be tested. This method is time
consuming.
Status of the Method: This method is a nonstandard test when used in rela-
tion to compaction control. However, periodic record sampling on compacted
embankments for dams usually entails obtaining block samples. In addition,
if the sample is properly removed from the fill, this test provides for index
and engineering properties.
Calibration Procedure: N/A
Documentation of Test: Items to be recorded include the sample's net weight
and net volume. An example data sheet is provided.
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Method No. 9
Parameter Measured: Unit Weight
Title of Test Method: Standard Laboratory Displacement
Principle of Test Method: This method determines the unit weight of a soil
sample by determining the weight of the sample and the volume of its hole.
Test Method
(1) Apparatus: Sampling tools, soil tray and pans, balances, measure,
drying equipment, two gallons of lubricating oil, and a gauge point.
(2) Procedure: This method determines the density of soil in-place by
finding the mass and water content of a disturbed sample and measuring the
volume occupied by the sample using an oil of a known density. The method
can be performed fairly fast, however a chief concern is the mess caused by
the oil. The general procedure consists of leveling the test site, digging a
hole in the compacted earthwork, weighing the material removed, measuring the
volume of the hole by placing a measured quantity of oil in it and calculating
the wet unit weight by dividing the weight of the moist soil by the volume of
the hole.
(3) Reference: AASHTO T 214.
Limitations: This method may be used in testing materials with both fine and
coarse particles; however, the test is best suited for soils and soil-
aggregate mixtures that are relatively impervious. The method may not be
suitable for testing materials having fissures, cracks, or large voids.
Status of the Method: The oil displacement method is a conventional test in
the control of earthwork construction. However, it often provides less
satisfactory results than the sand-cone method.
Calibration Procedure: N/A
Documentation of Test: Items to be recorded include the weight of the soil
sample and the volume of the oil. No example data sheet is provided.
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Method Noc 10
Parameter Measured: Unit Weight
Title of Test Method: Standard Field Sand-Cone
Principle of Test Method: This method determines unit weight by determining
the weight of a soil sample and the volume of its hole.
Test Method
(1) Apparatus: One gallon jar, double cone assembly, base plate and
accessories.
(2) Procedure: The test consists of digging out a sample of the mate-
rial to be tested and weighing it. The volume of the hole is then determined
by using the sand-cone.
(3) Reference: ASTM D 1556.
Limitations: The sand-cone has features which limit its usefulness. The
method can be used satisfactorily, however, if these limitations are recog-
nized and proper precautions observed. The poured density of sand is affected
by atmospheric moisture and changes in relative humidity which means the sand
should be calibrated before use. Care should be exercised to avoid jarring
and densifying the sand during the filling procedure and the test should not
be conducted during vibration of the site such as occurs during the use of
heavy equipment. Sample size is limited by sand supply.
Status of the Method: The sand-cone test is a conventional test method for
earthwork control. The method is reliable and the most commonly used test to
determine the density of in-place soil. On Corps of Engineers earthwork
projects the test serves as the referee test for all other control tests
used. The sand-cone test is widely used in cohesive soils and can be also
used in soils that are of low plasticity as well as gravelly soils. The
test is not applicable in clean sands or gravel and loose granular material.
The method is applicable to large and small projects.
Calibration Procedure: N/A
Documentation of Test: Items to be recorded include the weight of the soil
sample and the volume of the sand. No example data sheet is provided.
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Method No. 1
Parameter Measured: Water Content
Title of Test-Method: Standard Oven-Dry
Principle of Test Method: This method determines the water content of a soil
sample by first weighing it wet and then again after it has been dried in
an oven.
Test Method
(1) Apparatus: Drying oven (thermostatically controlled, preferably
of the force-draft type), balance sensitive to 0.01 g., specimen containers
(tares) with lids, and a desiccator.
(2) Procedure: The procedure for this method consists simply of taking
a specimen of known weight, placing it into an oven and drying it at a partic-
ular temperature and specified time. Upon drying the specimen is removed,
reweighed and the moisture content is calculated.
(3) Reference: ASTM D 2216.
Limitations: With many soils, close control of water content during field
compaction is necessary to develop a required density, strength and hydraulic
conductivity in the soil mass. Oven-drying is the standard test for deter-
mining water content of soils in the geotechnical engineering practice.
However, the method does not lend itself easily to field use. Although
temperature controlled ovens are currently available on some construction
sites, they require 4 to 12 hours for drying which may be excessive for the
close control of field compaction. All soils can be tested for moisture
content by oven-drying.
Status of the Method: Oven-drying of soil is the accepted laboratory method
among the geotechnical engineering profession for determination of water
content.
Calibration Procedure: N/A
Documentation of Test: Items to be recorded include the wet weight and the
dry weight. An example data sheet is provided.
125
-------
Naaet.
Date:.
.Sample Numbers,
. Sheet Number .
WATER CONTENT DETERMINATIONS
DATA AND COMPUTATION SHEET
NOTES! Tare is weight of container (watch glasses and clip, Petri dishes, can, etej
Water Content = w= wt* of
o ,
Wt. of Dry Soil
Sample Number
Type of Test
Container Number
Wt. Sample * Tare Wet
Wt. Sample + Tare Dry
Wt. of Water
Tare
Wt. of Dry Soil
Water Content
Sample Number
Type of Test
Container Number
Wt. Sample •*• Tare Wet
Wt. Sample +• Tare Dry
fft. of Water
Tare
Wt. of Dry Soil
Water Content
-
/
Sample Number
Type of Test
Container Number
Wt. Sample +• Tare Wet
Wt. Sample + Tare Dry
Wt. of Water
Tare
Wt. of Dry Soil
Water Content
126
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Method No. 2
Parameter Measured: Water Content
Title of Test Method: Standard Nuclear Moisture/Density Gage
Principle of Test Method: This method measures in place water content by
directing fast neutrons of known intensity into the soil and measuring the
intensity of slow or moderated neutrons reflected back.
Test Method
(1) Apparatus: Fast neutron source, slow neutron detector (readout
device and housing) and reference standard and site preparation device.
(2) Procedure: This method allows the determination of water content of
soil and soil aggregate in place through the use of nuclear equipment. The
equipment is calibrated to determine water content, as weight of water per
unit volume of material. Water content as normally used is defined as the
ratio, expressed as a percentage, of the weight of water in a given soil mass
to the weight of solid particles. It is determined with this procedure by
dividing the water content by the dry unit weight of the soil. Therefore,
computation of water content using the nuclear equipment also requires the
determination of the dry unit weight of the material being tested. Most
available nuclear equipment has the provision for measuring both the water
content and the wet unit weight. The difference between these two measurements
gives the dry unit weight.
(3) Reference: ASTM D 3017.
Limitations: The method described is useful as a rapid, nondestructive
technique for the in-place determination of the water content of soil. The
fundamental assumptions inherent in the method are that the hydrogen present
is in the form of water as defined by ASTM D 2216, and that the material
under test is homogeneous. Test results may be affected by chemical composi-
tion, sample heterogeneity, and, to a lesser degree, material density and the
surface texture of the material being tested. The technique also exhibits
spatial bias in that the apparatus is more sensitive to certain regions of
the material under test. The nuclear method, which is applicable to a wide
range of soils, requires operation by an experienced technician in order to
obtain reliable measurements. A weakness in the nuclear method is that a
sample is not taken to determine the water content, and thus the test results
cannot be compared to the other water content methods, e.g. the oven-dry method.
In addition, this method requires equipment that utilizes radioactive materials
which themselves may be hazardous to the health of the operator. Effective
operator instructions together with routine safety procedures are essential
to the proper operation of this type of equipment.
Status of the Method: Nuclear gages offer a rapid and accurate means for
obtaining water content values for a wide variety of soils. Recent advances in
the design of nuclear equipment and a better understanding of the nuclear
principles involved have led to increasingly widespread use of nuclear gages in
earthwork construction control.
127
-------
Calibration Procedure: The apparatus must be calibrated against a reliable
direct method (e.g. oven-drying).
Documentation of Test: Items to be recorded include the water content and the
wet unit weight. An example data sheet is provided.
128
-------
DATA SHEET FOR FIELD DENSITY TEST
| NUCLEAR GAUGE METHOD
A Moisture Standard Count
;
B j Density Standard Count
Gauge Type
FOR
JOB
SOURCE GP
MATERIAL
TEST LOCATION
ELEVATION
TEST NUMBER
C Moisture Count
D Moisture Count Ratio
E Density Count
Fi Air-Gap Count (if used)
6 ! Density Count Ratio
H j Density, Wet Wt,f "PCF
I Moisture Content, PCF
J ! Density, Dry Wt., PCF
K MOISTURE CONTENT, PERCENT
L OPTIMUM MOISTURE, PERCENT
M DENSITY, DRY WT., PCF
N THEORETICAL DENSITY, PCF
0 PERCENT COMPACTION
P REQUIRED PERCENT COMPAC.
Q j MODE & PROBE DEPTH, IN.
i
R TYPE OF MATERIAL ' '
v
/ \
/ \
C
A"
E • E '
F or F
From 6
i Chart
From D
& Chart
H - I
J
See Curve
From J
See Curve
f xlOO
See Specs.
Laboratory No. /yy
e
Serial No.
JOS NO.
DATE
:
•
Technician(s)
-------
Method No. 3
Parameter Measured: Water Content
Title of Test Method: Gas Burner
Principle of Test Method: This method determines the water content of a soil
sample by first weighing it wet and then again after it has been dried„
Test Method
(1) Apparatus: Gas stove, frying pan, balance and stirring rods,
(2) Procedure: This method determines the approximate water content of
soils by means of a gas-burner stove. The gas burner method involves the
weighing of a moist sample, placing the sample in a pan on the stove and
drying it to a constant weight, with occasional stirring of the sample to
prevent burning. The dry sample, first permitted to cool, is then reweighed
and the water content is determined.
(3) Reference: N/A
Limitations: The gas-burner method is used extensively for testing gravelly
material. Two or more samples may be tested concurrently. When care is
exercised to prevent overheating or burning of the sample, the testing time is
usually about 1/2 hour. The method is inaccurate for organic soils or for
those soils containing particles with loosely bound water, unless the drying
time is accomplished at a temperature of not more than 140°F (60°C) for 1 hour
or longer.
Status of the Method: The gas-burner method is used extensively as a rapid
method for testing gravelly soils in the field control of earthwork.
Calibration Procedure: N/A
Documentation of Test: Items to be recorded include the wet weight and the dry
weight. No example data sheet is provided.
130
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Method No. 4
Parameter Measured: Water Content
Title of Test Method: Alcohol Burning
Principle of Test Method: This method determines the water content of a soil
sample by first weighing it wet and then again after it has been dried by
alcohol burning.
Test Method
(1) Apparatus: Metal pan, balance, denatured alcohol and stirring rods.
(2) Procedure: This method determines the approximate water content of
soil by burning alcohol that has been added to the soil. The general procedure
consists of placing a weighted quantity of moist soil in a pan, adding alcohol
to it and stirring the mixture, then igniting the alcohol. After ignition and
the complete removal of the moisture by burning, the sample is reweighed and
its water content is calculated.
(3) Reference: N/A
Limitations: The alcohol burning test is a rapid inexpensive method for deter-
mining the water content of soils. The method is usable with non-cohesive and
cohesive soils. The method should not be used if the soil contains a large
proportion of clay, gypsum, calcareous matter or organic matter. A large
quantity of alcohol is required for testing coarse gravelly material. For
multiple burnings, the testing time can be in excess of 1/2 hour. In terms of
safety, the alcohol burning test possesses the potential for fire. Care should
be exercised not to have alcohol on hand or in an open storage container near the
testing apparatus during the ignition phase of the test. The alcohol should be
stored in a-safety container.
Status of the Method: The alcohol burning method of obtaining the water content
of soil in the field has provided satisfactory results. Its use in the field
has been well established.
Calibration Procedure: N/A
Documentation of Test: Items to be recorded include the wet weight and the
dry weight. No example data sheet is provided.
131
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Method No. 5
Parameter measured: Water Content
Title of Test Method: Calcium Carbide (Speedy)
Principle of Test Method: This method determines the water content of a soil
sample by measuring the pressure developed when measured quantities of the
soil sample and powdered calcium carbide are mixed.
Test Method
(1) Apparatus: Calcium carbide pressure moisture tester, tared scale,
two each 1-1/4 in. steel balls, brush, cloth and scoop.
(2) Procedure: The calcium carbide gas pressure method for determining
water content consists of mixing measured quantities of moist soil and powdered
calcium carbide in a closed chamber and measuring the pressure developed by
the formation of acetylene gas. The reaction of calcium carbide and water
forms acetylene gas and calcium hydroxide. The pressure developed is
directly related to the amount of water entering into the reaction.
(3) Reference: AASHTO T 217.
Limitations: Only two sizes of testers are commercially available to test
for water content using this method: (1) 26 gram capacity model and (2) a
six-gram capacity model. The small chamber capacities of these devices
control the soil sample size to be used. As a result, this method is unsuit-
able for representative samples of coarse granular material. AASHTO T 217
recommends that this method should not be used on.granular material having
particles large enough to affect the accuracy of the test (i.e. a soil with a
grain-size distribution such that an appreciable amount would be retained on
4.75 mm sieves). If a six-gram sample is used (according to AASHTO T 217),
the sample should not contain any particles that will be retained on the
2.00 mm sieve. The testing of heavy clays with this method requires special
handling.
Status of the Method: The apparatus for this method is relatively inexpen-
sive and well adapted to field testing. Use in the United States is extensive.
In the field the calcium carbide method has been used extensively in the
control of embankment construction. Normal testing time is less than 10 min.
A moderate amount of operator training is required. The calcium carbide
method is a standard method for rapid water content determination referenced
under AASHTO.
Calibration Procedure: A calibration curve is required.
Documentation of Test: Items to be recorded include soil sample weight,
powdered calcium carbide weight and the resultant gas pressure. No example
data sheet is provided.
132
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Method No. 6
Parameter Measured: Water Content
Title of Test Method: Microwave Oven
Principle of Test Method: This method determines the water content of a soil
by first weighing it wet and then again after it has been dried in the oven.
Test Method
(1) Apparatus: Microwave oven suitable for drying, balance, specimen
containers.
(2) Procedure: The procedure for this method is the same as that for
the Standard Oven-Dry method. That is, a specimen is placed wet onto a
balance and weighed. It is then placed in a microwave oven and dried
completely. It is then weighed again. The weight difference was the water
content.
(3) Reference: N/A
Limitations: Microwave ovens are not noted for their drying ability. There
are necessary safety precautions when using a microwave oven.
Status of the Method: This method is not commonly used. Although a microwave
oven heats much more rapidly than a conventional oven, it is an erratic dryer
at best. Thus this method should probably only be used to determine water
contents for soils which can be expected to have a low value, i.e. relatively
low water content.
Calibration Procedure: N/A
Documentation of Test: Items to be recorded include the wet weight and the
dry weight. No example data sheet is provided.
133
-------
Method No. 7
Parameter Measured: Water Content
Title of Test Method: Infrared Oven
Principle of Test Method: This method determines the water content of a soil
by first weighing it wet and then again after it has been dried in the oven.
Test Method
(1) Apparatus: Infrared oven suitable for drying, balance, specimen
containers.
(2) Procedure: The procedure for this method is the same as that for
the Standard Oven-Dry method. That is, a specimen is placed wet onto a
balance and weighed. It is then placed in an infrared oven and dried
completely. It is then weighed again. The weight difference was the water
content.
(3) Reference: N/A
Limitations: There are necessary safety precautions when using an infrared
oven. Infrared ovens are generally not widely available.
Status of the Method: This method is not commonly used. It can yield rapid
results, however. The method should be desirable to a large operation where
the benefits of rapid results outweigh the costs of the limitations above and
the initial investment.
Calibration Procedures N/A
Documentation of Test: Items to be recorded include the wet weight and the
dry weight. No example data sheet is provided.
134
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Method No. 8
Parameter Measured: Unit Weight
Title of Test Method: Standard Laboratory Volumetric
Principle of Test Method: This method determines the unit weight of an
undisturbed soil sample by measuring its weight and volume.
Test Method
(1) Apparatus: Sampling tools, balance, water bath, volume measuring
device, oven and coating material (e.g. paraffin).
(2) Procedure: This method determines the density of cohesive soil in
its natural state, compacted cohesive soil, ,and stabilized soil by measuring
the weight and volume of undisturbed samples. The method briefly consists of
cutting out a block of soil, coating it with a known amount of paraffin,
weighing to obtain the net weight of the sample and immersing it in an over-
flow volumeter to determine the net volume of the sample, then dividing
through for the unit weight.
(3) Reference: AASHTO T 233.
Limitations: The method is suitable for any material that remains intact
during sampling. This metod is particularly adaptable to irregularly shaped
specimens and soil containing gravel shells, etc. Sample size is not limited;
large samples with coarse aggregate can be tested. This method is time
consuming.
Status of the Method: This method is a nonstandard test when used in rela-
tion to comp_action control. However, periodic record sampling on compacted
embankments for dams usually entails obtaining block samples. In addition,
if the sample is properly removed from the fill, this test provides for index
and engineering properties.
Calibration Procedure: N/A
Documentation of Test: Items to be recorded include the sample's net weight
and net volume. An example data sheet is provided.
135
-------
UNIT WEIGHTS
PROJECT.
.LOCATION.
^TESTED BY.
SAMPLE NO.
ORIGINAL. SAMPLE SIZE
WT. CONTAINER + WET SOIL. GRAMS (W)
WT. CONTAINER * DRY SOIL. ORAMS (W*>
WT. MOISTURE, 0 RAMS (WwSW-W*)
WT. CONTAINER + ORY SOIL, GRAMS (V)
WT. CONTAINER, ORAMS (W*)
WT. ORY SOIL. ORAMS-CWssW'.w")
% MOISTURE, tWwaWw/W^aJOOl
ORY UNIT WT. I.BS./l'T.a
-•
SAMPLE NO.
ORIGINAL SAMPLE SIZE
WT. CONTAINER + WET SOIL. ORAMS (W>
WT. CONTAINER •»> DRY" SOIL. ORAMS (W1)
WT. MOISTURE, OftAMS (W^sW-Vj
WT. CONTAINER + DRY SOIL, ORAMS (w'»
WT. CONTAINER, 6RAMS (W*)
WT. ORY SOIL. ORAM3 (W,*w'-W*)
s MOISTURE". DRY SOIL. ORAMS
-------
Method No. 9
Parameter Measured: Unit Weight
Title of Test Method: Standard Laboratory Displacement
Principle of Test Method: This method determines the unit weight of a soil
sample by determining the weight of the sample and the volume of its hole.
Test Method
(1) Apparatus: Sampling tools, soil tray and pans, balances, measure,
drying equipment, two gallons of lubricating oil, and a gauge point.
(2) Procedure: This method determines the density of soil in-place by
finding the mass and water content of a disturbed sample and measuring the
volume occupied by the sample using an oil of a known density. The method
can be performed fairly fast, however a chief concern is the mess caused by
the oil. The general procedure consists of leveling the test site, digging a
hole in the compacted earthwork, weighing the material removed, measuring the
volume of the hole by placing a measured quantity of oil in it and calculating
the wet unit weight by dividing the weight of the moist soil by the volume of
the hole.
(3) Reference: AASHTO T 214.
Limitations: This method may be used in testing materials with both fine and
coarse particles; however, the test is best suited for soils and soil-
aggregate mixtures that are relatively impervious. The method may not be
suitable for testing materials having fissures, cracks, or large voids.
Status of the Method: The oil displacement method is a conventional test in
the control of earthwork construction. However, it often provides less
satisfactory results than the sand-cone method.
Calibration Procedure: N/A
Documentation of Test: Items to be recorded include the weight of the soil
sample and the volume of the oil. No example data sheet is provided.
137
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Method No. 10
Parameter Measured: Unit Weight
Title of Test Method: Standard Field Sand-Cone
Principle of Test Method: This method determines unit weight by determining
the weight of a soil sample and the volume of its hole.
Test Method
(1) Apparatus: One gallon jars double cone assembly, base plate and
accessories.
(2) Procedure: The test consists of digging out a sample of the mate-
rial to be tested and weighing it. The volume of the hole is then determined
by using the sand-cone.
(3) Reference: ASTM D 1556.
Limitations: The sand-cone has features which limit its usefulness. The
method can be used satisfactorily, however, if these limitations are recog-
nized and proper precautions observed. The poured density of sand is affected
by atmospheric moisture and changes in relative humidity which means the sand
should be calibrated before use. Care should be exercised to avoid jarring
and densifying the sand during the filling procedure and the test should not
be conducted during vibration of the site such as occurs during the use of
heavy equipment. Sample size is limited by sand supply.
Status of the Method: The sand-cone test is a conventional test method for
earthwork control. The method is reliable and the most commonly used test to
determine the density of in-place soil. On Corps of Engineers earthwork
projects the test serves as the referee test for all other control tests
used. The sand-cone test is widely used in cohesive soils and can be also
used in soils that are of low plasticity as well as gravelly soils. The
test is not applicable in clean sands or gravel and loose granular material.
The method is applicable to large and small projects.
Calibration Procedure: N/A
Documentation of Test: Items to be recorded include the weight of the soil
sample and the volume of the sand. No example data sheet is provided.
138
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Method No. 11
Parameter Measured: Unit Weight
Title of Test Method: Standard Field Rubber Balloon
Principle of Test Method: This method determines unit weight by determining
the weight of a soil sample and the volume of its hole.
Test Method
(1) Apparatus: Calibrated vessel, elastic membrane, pressure control
device, baseplate and accessories.
(2) Procedure: This method determines the in-place density by removing
soil from a hole, weighing the excavated material, and measuring the volume of
the hole by a liquid-filled (water) balloon under constant pressure. Chief
advantages of this method are its operation simplicity and speed with which
tests can be conducted.
(3) Reference: ASTM D 2167.
Limitations: For general use in clays and consolidated sands, the rubber
balloon apparatus provides good results. The method is not suitable for
very soft soil which will deform under slight pressure or in which the
volume of the hole cannot be maintained constant. The method is not well
adapted to the measurement of volumes in loose granular material. However, of
all in-place density tests some soil engineers recommend the water balloon as
the preferred method for granular soils. The tests is well adapted to small
and large projects. Physical limitation of the apparatus restricts the size
of the test hole to approximately four or six inches in diameter and from six to
twelve inches in depth.
Status of the Method: The water balloon test is widely used for determining
in-place density for the control of earthwork. The method is used by the
Corps of Engineers and other agencies because of its application to a wide
range of materials and its past performance record.
Calibration Procedure: N/A
Documentation of Test: Items to be recorded include the weight of the soil
sample and the volume of water. No example data sheet is provided.
139
-------
Method No. 12
Prameter Measured: Unit Weight
Title of Test Method: Standard Field Drive-Cylinder
Principle of Test Method: This method determines the unit weight of a soil
sample by securing one in a known-volume tube and then weighing it.
Test Method
(1) Apparatus: Acceptable drive cylinder, drive heads straightedges
shovel, weight, scales, drying oven and airtight containers.
(2) Procedure: The drive-cylinder method for determining in-place
density involves obtaining a relatively undisturbed soil sample by driving
a thin-walled cylinder into the soil with a special driving head. Two proce-
dures are described in ASTM D 2937 for performing this test, one for testing
at the surface or at very shallow depths, usually less than 3 ft (1 m), and
one for testing at greater depths. The general procedure for both depths
consists of driving a sampling tube into the soil, withdrawing the tube with
the sample, trimming the sample flush with the ends of the tube, weighing,
then calculating the unit weight of the soil by dividing the net weight of
the sample by the volume of the tube.
(3) Reference: ASTM D 2937.
Limitations: The drive-cylinder method of determining in-place density can
be used satisfactorily in moist, cohesive, fine-grained soils and in many
sands which exhibit tendencies toward cohesiveness. The method is not
appropriate for sampling very hard soils which cannot be penetrated easily,
or for soils_ of low plasticity which are not readily retained in the cylinder.
The method sample size is limited by the sample tube. The chief disadvantage
of the test is that it is limited to fine-grained soils.
Status of the Method: The standard field drive-cylinder method is a conven-
tional test method in earthwork control. It is, however, less accurate
than the sand cone or water balloon methods.
Calibration Procedure: N/A
Documentation of Test: Items to be recorded include the soil sample's weight.
No example data sheet is provided.
140
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Method No. 13
Parameter Measured: Unit Weight
Title of Test Method: Standard Nuclear Moisture/Density Gage
Principle of Test Method: This method determines unit weight by a gamma
source and a gamma detector.
Test Method
(1) Apparatus: A nuclear source emitting gamma rays, a gamma ray detector
and a counter.
(2) Procedure: This method determines the density of soil and soil-
aggregate in place through the use of nuclear equipment. In general, the
total or wet density of the material under test is determined by placing a
gamma source and a gamma detector either on, into, or adjacent to the material
under test. These variations in test geometry are presented as the back-
scatter, direct transmission, or air gap approaches. The intensity of radiation
detected is dependent in part upon the density of the material under test.
The radiation intensity reading is converted to measured wet density by a
suitable calibration curve. Some commonly used sources of gamma rays are
radium, cobalt 60 and cesium 137.
(3) Reference: ASTM D 2922.
Limitations: The method described is useful as a rapid, nondestructive tech-
nique for the in-place determination of the wet density of soils and soil-
aggregates. The fundamental assumptions inherent in the method are that
Compton scattering is the dominant interaction and that the material under
test is homogeneous. Test results may be affected by chemical composition,
sample heterogeneity, and the surface texture of the material being tested.
The technique also exhibits spatial bias in that the apparatus is more
sensitive to certain regions of the material under test. The nuclear method
is applicable to a wide range of soil. The nuclear method requires a con-
siderably experienced operator in order to obtain reliable measurements. A
weakness in the nuclear method is that a sample is not taken to determine the
water content, and thus the test results cannot be compared to another unit
weight method. In addition this method requires equipment that utilizes
radioactive materials which may be hazardous to the health of the operator.
Effective operator instructions together with routine safety procedures are
essential to the proper operation of this type of equipment.
Status of the Method: Nuclear gages offer a rapid and accurate means of
obtaining density values for a wide variety of materials. Recent advances in
the design of nuclear equipment and a better understanding of the nuclear
principles involved have led to increasingly widespread use of nuclear gages
in earthwork construction control.
Calibration Procedure: The apparatus must be calibrated against a reliable
direct method (e.g. standard field sand-cone).
141
-------
Documentation of Test: Items to be recorded include the counter's gamma ray
counts. No example data sheet is provided.
142
-------
Method No. 14
Parameter Measured: Specific Gravity
Title of Test Method: Standard Laboratory
Principle of Test Method: This method determines the specific gravity of a
soil sample by the use of a pycnometer.
Test Method
(1) Apparatus: A pycnometer and a balance.
(2) Procedure: The procedure for this method is to procure a soil
sample, weigh it with the balance, and then determines its specific gravity
by the use of the pycnometer.
(3) ASTM D 854.
Limitations: N/A
Status of the Method: This is the standard method. It is widely used.
Calibration Procedure: N/A
Documentation of Test: Items to be recorded include the sample weight and
the pycnometer reading. An example data sheet is provided.
143
-------
Names-
Sesple Numbers
Date:
Sheet Nuraber
SPECIFIC GRAVITY DETERMINATIONS
ample Number
Date:
Pycnometer Bottle Numbers_
Evapo Dish No,,
Wt. Bottle + Water +> Sample
Temperature of Suspension
= ».-
= T =_
Wt. Sample + Dish Dry-
Weight of Dish
Dry Wt. of Soil ffs
ww - wa
lem&rks;.
Sample Number.
Pyenometer1 Bottle number?,
Wt. Bottle + Water + Sample
sf Suspension
Dates
Ivap. Dish No
Wt. Sample +•
Weight, of Oiah
'WW-D
Remarkss
Sample Number.
Pycaometer Bottle Numbers
Wt. Bottle * Water + Sample
»« = .
Wt.
+• Water at temp. T = Ww=.
.Evap. Dieh No.
Wt« Sample + Dish Dry ~.
Weight of Dish =
Dry Wt. of Soil W0 =,
ff0 .
ffO * WW ~ ^8
leraarkas.
144
-------
Method No. 15
Parameter Measured: Grain-Size Distribution
Title of Test Method: Standard Sieve Analysis (+200 Fraction)
Principle of Test Method: This method determines the +200 fraction of a
soil sample by the use of a No. 200 sieve.
Test Method
(1) Apparatus: A No. 200 sieve, that is a sieve with 200 openings per
square inch, and balance.
(2) Procedure: This is a method dependent test. A dried soil sample
is weighed and poured onto a No. 200 sieve and shook. That amount of soil
not passing through the sieve is the +200 fraction. The +200 fraction is
then weighed on the balance.
(3) Reference: ASTM D 422.
Limitations: The limitations of the method are its possible sources of
error. These include: (a) overloading the sieve; (b) inadequate or incorrect
shaking; and (c) broken or damaged sieves.
Status of the Method: This is the standard method. It is widely used.
Calibration Procedure: N/A
Documentation of Test: Items to be documented include the weight of the
dried soil sample and the weight of the +200 fraction. An example data sheet
is provided.
145
-------
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-------
Method No. 16
Parameter Measured: Grain-Size Distribution
Title of Test Method: Amount of Soil Finer than No. 200 Screen (Wash)
Standard
Principle of Test Method: This method determines the -200 fraction of a
soil sample by the use of a No. 200 sieve and washing.
Test Method
(1) Apparatus: A No. 200 sieve and a balance.
(2) Procedure: This method is similar to that described for determining
the +200 fraction. However if the soil sample to be tested contains plastic
fines, drying will cause them to adhere to the fine sand grains, and the test
will yield erroneous results. The solution is to weigh the dry sample
beforehand. Pour it on the No. 200 screen. Wash the sample to loosen the
fines and allow them to pass through the sieve. Dry that amount of soil
remaining on the No. 200 screen and weigh it. The two weight differences is
then the fines content.
(3) Reference: ASTM D 422.
Limitations: The significant limitation of this method is the extra time
required for washing and redrying.
Status of the Method: This is the standard method. It is widely used.
Calibration Procedure: N/A
Documentation of Test: Items to be documented include the dry weight of the
sample and the dry weight of the +200 fraction. No example data sheet is
provided.
147
-------
Method No, 17
Parameter Measured: Grain-Size Distribution
Title of Test Method: Standard Laboratory Hydrometer (-200 Fraction)
Principle of Test Method: This method determines the grain-size distribution
of the -200 fraction of a soil sample by the use of Stokes' Law and a standard-
ized hydrometer.
Test Method
(1) Apparatus: A No. 200 sieve, a standardized hydrometer, a sedimenta-
tion cylinder, a thermometer and a breaker.
(2) Procedure: This method determines the grain-size distribution of
that fraction of a soil sample passing the No. 200 sieve (the -200 fraction).
The method utilizes a deflocculating (dispersing) agent and Stokes' Law
to enable the different particle sizes to settle at different rates, thus
enabling the technician to determine their distribution.
(3) Reference: ASTM D 422.
Limitations: An experienced technician is required to perform this test
method. Considerable time is required for sample preparation. The test
itself requires several hours to perform.
Status of the Method: This is the standard method. As it is the only
"exact" method for determining the percent silt sizes and the percent clay
sizes, it is widely used.
Calibration .Procedure: N/A
Documentation of Test: Items to be documented include the dry weight of the
sample and the dry weights of the settled fractions. Example data sheets
are provided.
148
-------
Date:
HYDROMETER ANALYSIS
DATA AND COMPUTATION SHEET
.Sample and Test Number,
__ Sheet Number.
Evaporating Dish No.
Wt. Sample + Dl<
Wt,
Dry wi
Hydrometer Numb<
Date
Time
-
»h Di-y so.
Wo 8-1
*r Meniacua Coi-p»f
Temp.
Elapsed
Time
H«
R=R» +c
. . . .
Grain
Dlam
(R * m)
(R * m)
(R + m)
tlon =r c =
R •*• m
V
Remarks
149
-------
Method No. 18
Parameter Measured: Grain-Size Distribution
Title of Test Method: Pipette Method for Silt and Clay Fraction
Principle of Test Method: This method determines the silt and clay fractions
of a soil sample by the use of a dispersing agent, Stokes' Law and a Pipette.
Test Method
(1) Apparatus: A No. 200 sieve, a beaker and a pipette.
(2) Procedure: The soil sample is deflocculated in a dispersing
agent for one hour. The soil-water-agent mixture is then agitated and allowed
to sit. Theroretically all the sand and silt sizes will have settled by
then. The water, with the suspended clay sizes, is then drawn off by the
pipette. The settled fraction is the original soil sample minus the clay
fraction. The settled fraction is completely dried and passed through a
No. 200 sieve. The fraction passing is the silt fraction, the fraction
remaining is the sand fraction.
(3) Reference: Mills, 1970.
Limitations: The method is less exact than the standard laboratory hydrometer
method.
Status of the Method: The method lends itself well to field laboratory use
and is widely accepted.
Calibration Procedure: N/A
Document at io'n of Test: Items to be documented include the dry weight of the
sample, the dry weight of the settled fraction and the dry weight of the
silt fraction. No example sheet is provided.
151
-------
o
1 — 1 51 — F
GRAIN SIZE DISTRIBUTION DIAGRAM
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-------
Method No. 19
Parameter Measured: Grain-Size Distribution
Title of Test Method: Decantation Method for Silt and Clay Fraction
Principle of Test Method: This method determines the silt and clay fractions
of a soil sample by the use of a dispersing agent. Stokes* Law and
decantation.
Test Method
(1) Apparatus: A No. 200 sieve and a beaker.
(2) Procedure: The soil sample is deflocculated in a dispersing agent
for one hour. The soil-water-agent mixture is then agitated and allowed to
sit. Theoretically all the sand and silt sizes will have settled by then.
The water, with the suspended clay sizes, is then drawn off by decantation
(careful pouring). The settled fraction is the original sample minus the
clay fraction. The settled fraction is completely dried and passed through
a No. 200 sieve yielding the silt fraction.
(3) Reference: Mills, 1970.
Limitations: The method is less exact than the standard laboratory hydrom-
eter method. As is also more rudimentary than the pipette method, it can
be less accurate than this method in execution.
Status of the Method: The method lends itself well to field laboratory use
and is widely accepted.
Calibration Procedure: N/A
Documentation of Test: Items to be documented include the dry weights of
the sample, the settled fraction and the silt fraction. No example sheet
is provided.
152
-------
Method No. 20
Parameter Measured: Liquid Limit
Title of Test Method: Standard Multipoint
Principle of Test Method: This method determines the liquid limit of a soil
sample by the use of the liquid limit device and a minimum of three trials.
Test Method
(1) Apparatus: Evaporating dish, spatula, liquid limit device, grooving
tool and balance.
(2) Procedure: A soil sample is oven dried. Distilled water is added
and mixed thoroughly with the sample till it is ready to be tested. A sample
is placed in the liquid limit device and divided by the grooving tool. The
test is run till the soil halves meet. The result is plotted. A minimum of
three trials are performed.
(3) Reference: ASTM D 423.
Limitations: The method requires considerable time and a laboratory environ-
ment to be performed.
Status of the Method: For the purposes needed at a hazardous waste disposal
facility the standard one point method will yield reasonable data with less
effort and hence is more widely used.
Calibration Procedure: N/A
Documentation of Test: Items to be recorded include the oven-dry weight of
the sample, the water content and the number of blows. An example data
sheet is provided.
153
-------
ATTERBERG LIMITS DETERMINATION
EXCAVAT10M MUM9IK
SAMPLE MUMSIS
LIQUID LIMIT, *L
RUN NUUBCR
T»»e MUM8E8
Ac WEIGHT OF WET SOIL * TA8£
8« WEIGHT Qf ORT SOIL t TARE
6. WEIGHT OF WATER, * (A. -8.)
0. WEIGHT OF TARE
1. »€!6Hf OF 8Rt SOIL.»,f»..0.)
r
WATER CQKTfNT, **(-g— " !ee)
NUU8ER OF SLOWS
"U
""
"f
., rvv
^ "-?
i«4 e
g
w *
^
5 t 1 t 9 10 15 20 25 SO
NUMBER OF SLOWS
PLASTIC LIMIT. *p
RUN NUU9CR
TARE NUMBER
F. wEISHt OF WET SOIL + TARE
G. WEIGHT OF ORT SOIL + TARE
H. WEIGHT OF WATER, *„ (F.-a.)
t, WEIGHT OF TARE
J. WEIGHT OF ORT SOIL. *S(
-------
Method No. 21
Parameter Measured: Liquid Limit
Title of Test Method: Standard One Point
Principle of Test Method: This method determines the liquid limit of a soil
sample by the use of the liquid limit device and one trial.
Test Method
(1) Apparatus: Evaporating dish, spatula, liquid limit device, grooving
tool and balance.
(2) Procedure: A soil sample is oven dried. Distilled water is added
and mixed thoroughly with the sample till it is ready to be tested. A sample
is placed in the liquid limit device and divided by the grooving tool. The
test trial is then run till the soil halves meet. The data is then plotted.
(3) Reference: ASTM D 423.
Limitations: The method requires considerable time and a laboratory environ-
ment to be performed.
Status of the Method: The method is more widely used than the standard
multipoint method, but as it is a correlation test method and it is usually
used in soil identification, it is often less practical than the commonly
used visual-manual procedure (ASTM D 2488).
Calibration Procedure: N/A
Documentation of Test: Items to be recorded include the oven-dry weight of
the sample, the water content and the number of blows. No example data
sheet is provided.
155
-------
Method No. 22
Parameter Measured: Plastic Limit
Title of Test Method: Standard Laboratory
Principle of Test Method: This method determines the plastic limit of a soil
sample, that is the lowest water content at which the soil can be rolled into
1/8 in. threads without breaking.
Test Method
(1) Apparatus: Evaporating dish, spatula, suitable containers, and
balance.
(2) Procedure: For a given soil sample begin at a water content esti-
mated to be greater than that at the plastic limit. A good start point would
be the approximate liquid limit. Shape the soil into an ellipsoidal mass.
Roll the sample into 1/8 in. threads. Cut the threads into 6 to 8 pieces.
Repeat the process till the threads break at 1/8 in. An oven-dry moisture
content determination at that point will yield the plastic limit.
(3) Reference: ASTM D 424.
Limitations: The method is simple and straightforward.
Status of the Method: This is the standard method and is widely used.
Calibration Procedure: N/A
Documentation of Test: Items to be recorded include the oven-dry and wet
weight of the sample at the plastic limit. An example data sheet is
provided.
156
-------
ATTERBERG LIMITS
SAMPLE N2
PROJECT.
DATE.
SOURCE OF SAMPLE
SUMMARY
NATURAL
WATER CONTENT
LIQUID
LIMIT
PLASTIC
LIMIT
PLASTICITY
INDEX
SHRINKAGE
LIMIT
.
PLASTIC LIMIT
NATURAL WATER CONTENT
DETERMINATION N«
CONTAINER N*
CONTAINER 4- WET SOIL
CONTAINER + DRY SOIL
WEIGHT OF WATER
CONTAINER + DRY SOIL
WEIGHT OF CONTAINER
WEIGHT OF DRY SOIL
PERCENT WATER
1 -
2.
3
t
1
2.
3
LIQUID LIMIT
DETERMINATION N«
NUMBER OF BLOWS
CONTAINER NS
CONTAINER 4- WET SOIL
CONTAINER 4- DRY SOIL
WEIGHT 'OF WATER
CONTAINER 4- DRY SOIL
WEIGHT OF CONTAINER
WEIGHT OF DRY SOIL
PERCENT WATER
1
Z
3
4
5
6
t
s
H
Z
til
Ul
K.
CO
O
TESTED BY
tin
20 23 30 4O SO 60 70 80 SO iOO
NUMBER OF BLOWS
Reproduced from
best available copy.
157
-------
Method No. 23
Parameter Measured: Cohesive Soil Consistency
Title of Test Method: Standard Unconfined Compression
Principle of Test Method: This method uses a compression device to determine
the unconfined compressive strength of a soil sample: that is the load per
unit area at which the specimen fails in simple compression.
Test Method
(1) Apparatus: Compression device, sample ejector, deformation indi-
cator, vernier caliper, timer, balance and oven.
(2) Procedure: An unidsturbed sample is secured and a specimen prepared
as per the reference. An estimate of the failure strength is made based on
experience with a similar material. The specimen is placed in compression by
uniformly progressive loads at 30 second intervals till failure or 20% strain
is reached. The results are plotted.
(3) Reference: ASTM D 2166.
Limitations: The method requires a laboratory environment, the securing of
an undisturbed sample (as described by ASTM Method D 1587), considerable
specimen preparation, calculations and considerable time.
Status of the Method: The method is the standard means for unconfined com-
pressive strength determination. However because of its limitations it is
not commonly used in process control (because of more efficient methods) but
is widely used in acceptance testing.
Calibration Procedure: The deformation indicator must be zeroed at the
beginning of the test.
Documentation of Test: Items to be recorded include the water content of the
sample as well as the strain deformations at their respective loads. An
example data sheet is provided.
158
-------
UNCONFINED COMPRESSION TEST - DATA SHEET
LL *?. w '
Didmetar* in Initial
Prnjart
Labornlnry
i PL % DntB Tested
tsf Spefific Grovity, Gs DfY Unit Weight, Xj ,. .
Soil Specimen Measurements
A'»"r AO; .. *f Initial Length, LO:
pef
in
WATER CONTENT
Specimen Location
Container No.
Wt. Cont. + Wet SoiKgms.)
Wt. Cont. + Dry Soil(gms-)
Wt. Container (gins.)
Wt. Dry Soil(gms.)
Wt. Water(gms.)
Water Content(%)
Top
Middle
Bottom
Entire Remolded Sample
COMPRESSION TEST
Elapsed Time
(Min.)
-
Load Dial
Reading
Load
(Ibs.)
' Vert. Dial
(inches)
/*"?
Axial Strain £
(7.)
Corr. Area, A{
(sf)
Camp. Stress, Sc
«P*f)
-------
Method No. 24
Parameter Measured: Cohesive Soil Consistency
Title of Test Method: Field Expedient Unconfined Compression
Principle of Test Method: This method uses a field expedient compression
device to determine the unconfined compressive strength of a soil sample.
Test Method
(1) Apparatus: Sample selector, compression device, stress and
deformation indicators, balance, oven and trimmer.
(2) Procedure: A sample is secured and prepared. An estimate of the
sample's failure strength is made based on experience with a similar material.
The specimen is then placed in compression by uniformly progressive loads
till failure or a predetermined percent strain is achieved. The results
are plotted.
(3) Reference: TM 5-530, 1971.
Limitations: The method involves a procedure virtually identical to that
called for in the standard laboratory method. However the apparatus used
in the field expedient method is less accurate, less care is given to
sample preparation and the method itself is less accurate.
Status of the Method: The method lies between the standard laboratory
method and the hand device methods in terms of accuracy and resources
required. As the standard laboratory method is the accepted method for
laboratory needs and the hand devices are sufficient for field testing. This
method is not widely used.
Calibration Procedure: The stress and strain indicators must be zeroed at
the beginning of the test.
Documentation of Test: Items to be recorded include the sample's water
content as well as the stress and strain readings. No example data sheet
is provided.
160
-------
Method No. 25
Parameter Measured: Cohesive Soil Consistency
Title of Test Method: Hand Penetrometer
Principle of Test Method: This method uses the hand penetrometer to deter-
mine the unconfined compressive strength of a soil sample.
"Test Method
(1) Apparatus: Hand penetrometer with stress and strain indicators,
trimming knife.
(2) Procedure: A sample is taken and trimmed by the hand penetrometer
and a trimming knife. The test is then run with the device. One man can run
the device and read the various stress and strain indicators. These values
can be plotted and the unconfined compressive strength determined.
(3) Reference: Hvorslev, 1943.
Limitations: The sampling operation may cause a slight disturbance and
decrease in strength of very brittle soils, a small downward deflection of
soft soils, and a slight compaction of loose and partially saturated soils.
Status of the Method: The determination of cohesive soil consistency classi-
fication by this method is widely used as it is more accurate than the
visual-manual method, and although it is less accurate than the standard
laboratory method it is quite sufficient given the broad classifications for
cohesive soil consistency.
Calibration Procedure: The stress and strain indicators must be zeroed at
the beginning of the test.
Documentation of Test: Items to be recorded include the stress and strain
readings during testing. An example data sheet is provided.
161
-------
UNCONF1NED COMPRESSION TEST
Soil Description.
Project.
•laboratory.
Bering Mo.
U _%
Surface £ie».
%
_S
-------
Method No. 26
Parameter Measured: Cohesive Soil Consistency
Title of Test Method: Handheld Torvane
Principle of Test Method: This method uses a handheld torvane to determine
the soil shear strength of the in situ soil.
Test Method
(1) Apparatus: Handheld torvane with gage.
(2) Procedure: The handheld torvane is pushed through the soil crust to
the desired depth. A rotary motion is then applied to the handle. The gage
values are read and the soil shear strength, values for cohesion and the
internal angle of friction, and consistency classification can be determined.
(3) Reference: Lanz, 1968.
Limitations: The method is standardized and the values gained from the method
can be correlated to the standard laboratory method for unconfined compres-
sive strength. However the method is somewhat less accurate than others.
Status of the Method: The torvane is the most widely accepted of the shear
vane devices. Since it yields in situ values rapidly it is widely used.
Calibration Procedure: The gage must be zeroed before testing.
Documentation of Test: Items to be recorded include the gage readings. No
example data sheet is included.
163
-------
Method No, 27
Parameter Measured: Water Content/Density/Compactive Effort
Title of Test Method: 25 Blow Standard Proctor Compaction
Principle of Test'Method: This method determines the optimum moisture content
and the maximum density of a soil sample by an impact compaction test. This
is the original Proctor test.
Test Method
(1) Apparatus: Molds, rammer, extruder, balance, drying oven, sieves.
(2) Procedure: The specimen is prepared and placed in a mold. Most
commonly the mold is the 4 inch mold. The soil is placed in three like
layers. Each layer is compacted. Most commonly the compaction is 25 blows
with a 5.5 pound hammer dropping 12 inches. Following compaction of all
three layers the specimen is removed from the mold and trimmed. The mass of
the sample is determined. This is divided by the volume of the mold and then
the wet density of the sample, in pcf, is determined. The water content of
the sample is then determined by oven drying. This entire procedure is
repeated for at least four specimens. The four specimens' water contents
should vary by about 1-1/2% between each sequential sample. The specimen
water contents should bracket the estimated optimum moisture content. The
values are plotted along with the "zero air voids curve." The optimum
moisture content and maximum density of the sample can then be determined.
(3) Reference: ASTM D 698.
Limitations: This method requires a laboratory environment, the considerable
time involved in sample drying and several hours to perform the test itself.
Status of the Method: This is the standard method. It is widely used. It
is suited for the lesser compactive effort as might be applied to trench
backfill. It may not be as suitable as the modified method for higher
compactive efforts such as that which might be applied to a trench floor.
Calibration Procedure: The rammer must be calibrated before initial use and
again after each 1,000 molds.
Documentation of Test: Items to be recorded include the mold volumes, speci-
men masses, and specimen water contents. An example data sheet is provided.
164
-------
SOILS LABORATORY COMPACTION TESTS PROCTOR METHOD . Sample No.
SITE
HOLE
AREA
DEPTH
RUN
NO.
1
2
3
4
5
6
7
8
9
10
11
12
13
WEIGHT OF
SAMPLE +
CYLINDER
KG.
WEIGHT
OF
CYLINDER
KG.
WEIGHT
OF
SAMPLE
KG.
TESTED BY: . DA"
WEIGHT OF
SAMPLE
LBS./CU. FT.
re
COMPUTED BY: DATE
WATER
ADDED
GRAMS
NUMDER OF BLOWS
PLASTIC LIMIT
SPECIFIC GRAVITY
DATE
WATCH
GLASS
NO.
WATER
CONTENT
%
DRY WT.
CYLINDER NO.
VOL. OF CYLINDER CU. FT,
UNIT WEIGHT FACTOR
REMARKS ,
.
CHECKED BY:
DATE
-------
Method No. 28
Parameter Measured: Water Content/Density/Compactive Effort
Title of Test Method: 25 Blow Modified Proctor Compaction
Principle of Test Method: This method determines the optimum moisture content
and the maximum density of a soil sample by an impact compaction test.
Test Method
(1) Apparatus: Molds, rammer, extruder, balance, drying oven, sieves.
(2) Procedure: The specimen is prepared and placed in a mold in three
like layers. The mold most commonly used is the four inch mold. Each layer
is compacted. The compaction used for the four inch mold is 25 blows with
a 10 pound hammer dropping 18 inches. Following compaction of all three
layers the specimen is removed from the mold and trimmed. The mass of the
sample is determined. This is divided by the volume of the mold and then the
wet density of the sample, in pcf, is determined. The water content of the
sample is then determined by oven drying. The entire procedure is repeated
for at least four specimens. The four specimens' water contents should vary
sequentially by about 1-1/2 percent. The specimen water contents should
bracket the estimated optimum moisture content. The values are plotted along
with the "zero air voids curve." The optimum moisture content and maximum
density of the sample can then be determined.
(3) Reference: ASTM D 1557.
Limitations: This method requires a laboratory environment, the considerable
time involved in sample drying and several hours to perform the test itself.
Status of the Method: This is also a standard method. It is widely used.
As it better represents greater compactive effort than does the original
Proctor test, it is more suitable for process control testing for trench
floors and the like.
Calibration Procedure: The rammer must be calibrated before initial use and
again after each 1,000 molds.
Documentation of Test: Items to be recorded include the mold volumes, speci-
men masses, and specimen water contents. No example data sheet is provided.
166
-------
Method No. 29
Parameter Measured: Water Content/Density/Compactive Effort
Title of Test Methods: Nonstandardized Proctor Compaction
Principle of Test Methods: These methods determine the optimum moisture
content and the maximum density of a soil sample by kneading compaction,
static compression or other devices.
Test Methods
(1) Apparatus: Molds, sieves, balance, drying oven, extruder, kneading
device or static compression device.
(2) Procedure: The procedures are method specific. (See the references.)
However the procedures are very similar to the standard laboratory methods.
Only the nature of the compactive effort and the specifics of the mold
size, etc., differ.
(3) Reference: Johnson and Sallberg, 1962; and Antrim, 1970.
Limitations: These methods require a laboratory environment, the considerable
time involved in sample drying and several hours to perform the tests
themselves.
Status of the Method: These are not standard laboratory methods. They were
developed for use in special situations. They are used by several state
highway departments.. They are not widely used in the laboratory because of
the preference for the standard methods or in the field because of the ease
and sufficiency of other methods^
Calibration Procedure: See the references.
Documentation of Test: Items to be recorded include the mold volumes, speci-
men masses, and specimen water contents. No example data sheet is provided.
167
-------
Method No. 30
Parameter Measured: Water Content/Density/Compactive Effort
Title of Test Method: Rapid, One Point Proctor Compaction
Principle of Test Method: This method determines the optimum moisture content
and the maximum density of a soil sample by an impact compaction test and
estimation, given one specimen test and its derived value.
Test Method
(1) Apparatus: Molds, rammer, extruder, balance, drying oven, sieves.
(2) Procedure: The procedure is essentially the same as that for the
standard laboratory method. However, rather than running four or more
(usually the number is five) specimens through the test and deriving a like
number of points, only one test is run and one point is derived. The one
point is at a water content estimated to be on the dry side of the optimum.
From this point, and the well documented data on the soil, the optimum moisture
content and maximum density can be determined.
(3) Reference: EM 1110-2-1911, 1977.
Limitations: This method depends upon good and well documented data on the
local soils. The method also depends upon data which defines a relatively
good line of optimums.
Status of the Method.: For suitable soils this method provides a much more
rapid means of process control. It is widely used. It is probable that this
method could be sufficiently applied to the compaction of trench backfill.
Calibration Procedure: The rammer must be calibrated before initial use and
again after each 1,000 molds.
Documentation of Test: Items to be recorded include the mold volumes, speci-
men masses, and specimen water contents. No example data sheet is provided.
168
-------
Method No. 31
Parameter Measured: Water Content/Density/Compactive Effort
Title of Test Method: Rapid, Two Point Proctor Compaction
Principle of Test Method: This method determines the optimum moisture content
and the maximum density of a soil sample by an impact compaction test and
estimation, given two specimen tests and their derived values.
Test Method
(1) Apparatus: Molds, rammer, extruder, balance, drying oven, sieves.
(2) Procedure: The procedure is essentially the same as that for the
standard laboratory method. However, rather than running four or more
(usually the number is five) specimens through the test and deriving a like
number of points, only two tests are run and two points are derived. The
first test is with a specimen estimated to be at the optimum moisture content
or just on the dry side of the optimum. The second test is with a specimen 2
or 3 percentage points dry of the water content of the first specimen. From
these points, and the well documented data on the soil, the optimum moisture
content and maximum density can be determined.
(3) Reference: EM 1110-2-1911, 1977.
Limitations: This method depends upon good and well documented data on the
local soils. The method also depends upon data which defines a relatively
good line of optimums.
Status of the Method: In this method two curves are developed, as opposed
to one curve as in the one point method, thus this method can be expected to
yield a better estimated curve. As this method provides more accuracy than
the one point method, it is perhaps even more applicable to trench backfill
compaction process control.
Calibration Procedure: The rammer must be calibrated before initial use and
again after each 1,000 molds.
Documentation of Test: Items to be recorded include the mold volumes, speci-
men masses, and specimen water contents. No example data sheet is provided.
169
-------
Method No. 32
Parameter Measured: Water Content/Density/Compactive Effort
Title of Test Method; Hilf's Rapid
Principle of Test Method: This method determines the optimum moisture content
and the maximum density of a soil sample by the standard impact compaction
test of three samples, the use of standardized forms, and an estimate of the
optimum moisture content.
Test Method
(1) Apparatus: Molds, rammer, extruder, balance, drying oven, sieves.
(2) Procedure: The procedure utilizes the standard impact compaction
test. Three samples are tested. The first sample is that at field moisture,
a water content estimated to be on the dry side of optimum. The second
and third samples are tested at water contents two and four percent more
than the field moisture. The derived values are compared to standardized
forms and plotted. Without determination of water content, the maximum
density and difference of the field moisture from the optimum content can
then be determined. This is done by connecting the plotted points, which
bracket the optimum moisture content, and thus yield its value.
(3) Reference: Hilf, 1970.
Limitations: This method is only suitable for low plasticity cohesive soils.
Status of the Method: When applicable this method yields sufficient data
in much less time than the standard impact tests. However, because it yields
only an approximation of the optimum moisture content its applicability is
limited.
Calibration Procedure: The rammer must be calibrated before initial use and
again after each 1,000 molds.
Documentation of Test: Items to be recorded include the mold volumes, speci-
men masses, and specimen water contents. No example data sheet is provided.
170
-------
Method No. 33
Parameter Measured: Water Content/Density/Compactlve Effort
Title of Test Method: Ohio Highway Department Nest of Curves
Principle of Test Method: This method determines the optimum moisture content
and the maximum density of a. soil sample by the standard impact compaction
test yielding one point, and its placement on a nest of curves for like soils.
Test Method
(1) Apparatus: Molds, rammer, extruder, balance, drying oven, sieves,
circular slide rule.
(2) Procedure: A single test is performed as per one of the standard
impact compaction methods. The derived point is then matched to a nest of
curves. For field expedience this nest of curves is often contained on a
circular slide rule. The optimum moisture content and maximum density are
then estimated from the appropriate curve.
(3) Reference: Ohio Highway Department, 1958.
Limitations: This method depends upon good and well documented data on the
local soils.
Status of the Method: Where a nest of curves exists this method is a rapid
means of determining the optimum moisture content and maximum density. It
has proven to be sufficient in a widespread history of usage.
Calibration Procedure: The rammer must be calibrated before initial use and
again after_each 1,000 molds.
Documentation of Test: Items to be recorded include the mold volumes, speci-
men masses, and specimen water contents. No example data sheet is provided.
171
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Method No. 34
Parameter Measured: Water Content/Density/Compactive Effort
Title of Test Method: Harvard Miniature Compaction
Principle of Test Method: This method determines the optimum moisture content
and the maximum density of a soil sample by a kneading compaction test with
the Harvard Miniature device.
Test Method
(1) Apparatus: Molds, tampers extruder, balance, drying oven, sieves.
(2) Procedure: The procedure utilizes different apparatus than does
the standard impact compaction test. Also this procedure utilizes kneading
as opposed to impact compaction. Other than that, with the exception of
specifics, the procedures are quite similar. This procedure is readily
adaptable to better represent the actual field compactive efforts to be
achieved.
(3) Reference: Wilson, 1970.
Limitations: This method is suitable only for soils passing the No. 4
screen. Thus it is applicable for usage at a hazardous waste disposal
facility.
Status of the Method: The method is small in terms of apparatus cost and
size, simple, adaptable to duplicate the compactive effort achieved by
larger equipment and ideal for field laboratory use. For better representing
the actual field compactive efforts to be achieved the kneading action of the
Harvard Miniature apparatus is superior to the impact action of the impact
devices.
Calibration Procedure: N/A
Documentation of Test: Items to be recorded include the mold volumes, speci-
men masses, and specimen water contents. No example data sheet is provided.
172
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Method No. 35
Parameter Measured: Cohesionless Soil Relative Density
Title of Test Method: Standard Laboratory Maximum Density
Principle of Test Method: This method determines the maximum relative density
of a cohesionless soil sample by the use of a vibratory table.
Test Method
(1) Apparatus: Vibratory table, molds, dial indicator, calibration bar,
scale, other related equipment.
(2) Procedure: A soil sample is oven dried. The sample is thoroughly
mixed. The sample is placed in a mold with a surcharge weight. The mold is
vibrated for 8 minutes. The volume of the densified soil sample within the
mold is determined. The sample is weighed. The maximum relative density can
then be determined.
(3) Reference: ASTM D 2049.
Limitations: The method requires a vibratory table. This item is not often
found on field sites.
Status of the Method: The method is the standard method and is widely used
for laboratory purposes. The provision exists for a wet method in the
reference.
Calibration Procedure: The exact mold volume must be determined and the
dial must be zeroed before the test.
Documentation of Test: Items to be recorded include the mold volume and the
dry weight of the sample. An example data sheet is provided.
173
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174
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Method No. 36
Parameter Measured: Cohesionless Soil Relative Density
Title of Test Method: Standard Laboratory Minimum Density
Principle of Test Method: This method determines the minimum relative density
of a cohesionless soil sample by the standard method.
Test Method
(1) Apparatus: Molds, pouring devices, 3/8 in. sieve, and straight edge*
(2) Procedure: A soil sample is oven dried. The soil is segregated
into a +3/8 in. and a -3/8 in. fraction by passing through the sieve. Each
fraction is carefully poured to overflowing into pre-measured molds. The
excess soil is screed off. The soil fractions are weighed and the minimum
relative density determined.
(3) Reference: ASTM D 2049.
Limitations: The method depends upon the technician's ability to carefully
pour the segregated soil sample into the molds and his ability to scree off
the excess with minimum effect to the soil in the molds.
Status of the Method: The method is the standard method and is widely
used. It lends itself well to field site usage.
Calibration Procedure: The exact mold volume must be determined before the
test.
Documentation of Test: Items to be recorded include the mold volumes and
the soil fraction weights. No example data sheet is provided.
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Method No. 37
Parmater Measured: Cohesionless Soil Relative Density
Title of Test Method: Modified Providence
Principle of Test Method: This method determines the maximum relative density
of a cohesionless soil sample by the use of a hammer.
Test Method
(1) Apparatus: Molds dial indicator, hammer, balance.
(2) Procedure: A soil sample is oven dried and thoroughly mixed. It
is placed in a mold and a surcharge weight equivalent to 1 psi is applied.
The mold is struck uniformly by a hammer in the specified fashion till the
dial reading changes less than 0.005 inches for any 25 blow cycle. The
sample is then measured.
(3) Reference: EM 1110-2-1906, 1970.
Limitations: A nonuniform distribution of the hammer blows over the height
and circumference of the mold may cause error in the determination of the
maximum relative density.
Status of the Method: The method is not as accurate as the standard labora-
tory method. However, because no vibratory table is required and because
the method's accuracy is sufficient for process controls the method is
widely used at field sites.
Calibration Procedure: The exact mold volume must be determined and the
dial must be zeroed before the test.
Documentation of Test: Items to be recorded include the mold volume and
the dry weight of the sample after testing. No example data sheet is provided.
176
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Method No. 38
Parameter Measured: Geomembrane/Geotextile Seam Integrity
Title of Test Method: Bonded Seam Strength
Principle of Test Method: This method tests the seam strength of a specimen
by placing it in tension and measuring its modulus of elasticity.
Test Method
(1) Apparatus: Grips, thickness gage, width-measuring devices, specimen
cutter, extension indicators and a rate-of-jaw separation testing machine.
(2) Procedure: A specimen of a bonded seam is cut and measured and
placed in the machine perpendicular to the center line. The specimen is
then placed in tension. The same is done for a specimen of the sheet itself.
The tensile modulus of elasticity for both are calculated. The bonded seam
strength can then be calculated as a percentage of the sheet strength.
(3) Reference: ASTM D 3083.
Limitations: This method requires a qualified test conductor, the apparatus
described and a "sheltered" environment to yield significant accuracy. A
deficiency in any of these requirements would limit the validity of the
method.
Status of the Method: This method is probably not applicable to all quality
assurance programs for hazardous waste disposal facilities. The apparatus,
"sheltered" environment and qualified test conductor may be too much for a
small operation. The equipment needed is also expensive and another method
might prove _to be more economical. Modified methods, the results of which
correlate to this standard method, have been developed and are proving
acceptable. These modified methods do not require the "sheltered" environ-
ment or as elaborate apparatus.
Calibration Procedure: See the reference.
Documentation of Test: Items to be recorded include specimen dimensions,
exact loading versus time and elongation versus time. No example data sheet
is provided.
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Method No. 39
Parameter Measured: Geomembrane/Geotextile Seam Integrity
Title of Test Method: Breaking Strength
Principle of Test Method: This method tests the breaking strength of speci-
mens by placing them in tension in two transverse directions till they break.
Test Method
(1) Apparatus: Straining mechanism, clamps for holding specimen, and
load and elongation recording mechanisms.
(2) Procedure: At least ten specimens of a bonded seam should be cut
and measured (if one of the tests is invalid another specimen must be tested
to yield a total of ten tests). The specimens are placed longitudinally in
the clamps and strained till they break. Specimens should be strained till
breakage in both the parallel and perpendicular to the seam directions. The
average of five valid tests is the breaking strength of the seam in that
direction.
(3) Reference: ASTM D 751.
Limitations: The specimens can tear or slip at the clamps.
Status of the Method: This method is probably not applicable to all quality
assurance programs for hazardous waste disposal facilities. The ten or more
specimens required are considerable. The equipment needed is relatively
expensive yet very accurate. Electric power is required. However for a large
operation the method may be applicable as it yields accurate, valid data in a
short time. Modified methods, the results of which correlate to this standard
method, have been developed and are proving acceptable. These modified methods
do not require the "sheltered" environment or as elaborate equipment.
Calibration Procedure: See the reference.
Documentation of Test: Items to be recorded include specimen dimensions,
exact loading versus time, elongation versus time, and loading at breakage.
No example data sheet is provided.
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Method No. 40
Parameter Measured: Geomembrane/Geotextile Seam Integrity
Title of Test Method: Peel Adhesion
Principle of Test Method: This method tests the peel adhesion of a specimen
by measuring the force it takes to peel apart a bonded seam.
Test Method
(1) Apparatus: A CRE or CRT-type, power driven, tension testing
machine; or a frame and mandrels for the Static-Mass Method.
(2) Procedure: A specimen of a bonded seam is cut and measured. At
one end of the specimen the parts are separated. The separated parts are
attached to the machine. The tension on the separated parts is increased
till failure. All forces and separations are carefully measured.
(3) Reference: ASTM D 413.
Limitations: A CRE or CRT-type machine requires power. A frame and mandrels
set is inexpensive but is also uncommon to many construction site field
testing facilities. Tearing of one or both of the separate parts of the
specimen during loading is a hazard.
Status of the Method: Because of its ease and simplicity this test is
applicable to a quality assurance program for a hazardous waste disposal
facility. The frame and mandrels set are inexpensive. The test method does
not require a "sheltered" environment beyond what most construction site field
testing facilities provide.
Calibration Procedure: See the reference.
Documentation of Test: Items to be recorded include specimen dimensions,
exact loading forces versus time and separations versus time. No example data
sheet is provided.
179
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Method Noo 41
Parameter Measured: Geomembrane/Geotextile Seam Integrity
Title of Test Method: Air Lance
Principle of Test Method: This method tests the bond of a seam by detecting
anomalies with a jet of compressed air.
Test Method
(1) Apparatus: A source of compressed air (40-60 psi)s a wand pipe
narrow tip nozzle (e.g. 3/16 in.).
(2) Procedure: One man walks the length of the bonded seams pointing
the nozzle and air jet at the edge of the top flap, within one inch of the
same, with the nozzle parallel to the edge. A bubble will form under any
unbonded edges. The results of such a bubble will be both audible and visual.
(3) Reference: N/A
Limitations: The method should be conducted with specimen testing (see test
methods 38, 39 and 40) to assure field seam integrity and reliability. The
method may not detect small anomalies.
Status of the Method: The method is applicable to a quality assurance program
as a relatively rapid and rough determination of seam integrity. It should
be conducted along with specimen testing. Its advantages over methods 42
and 43 are its ease, speed and economy. Its disadvantage is its rough
detection capability. It will not detect pinholes. But where complete
bonding is the critical determination, such as might be the case in an
installed geomembrane used as part of a trench cover system, this method may
be sufficient by itself.
Calibration Procedure: N/A
Documentation of Test: Items to be recorded include the detection and
location, as well as marking of all anomalies. No example data sheet is
provided.
180
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Method No. 42
Parameter Measured: Geomembrane/Geotextile Seam Integrity
Title of Test Method: Vacuum Box
Principle of Test Method: The method detects leaks in the seam by means of a
vacuum.
Test Method
(1) Apparatus: Vacuum pump, power plant, inspection box, vacuum guage,
soap, gasket.
(2) Procedure: The seam is lathered with soap to form a tight fit with
the gasket. The inspection box is passed over the seam and it will detect any
leaks to include those of pinhole size. The method tests seam integrity by
detecting leaks. It does not test seam strength.
(3) Reference: Copywright by American Pipe & Steel Corporation.
Limitations: This method was developed for testing metal tanks and other
similar containers. Because it is labor intensive, and because of the con-
siderable time required, the method does not lend itself to expedient seam
integrity testing. The length of a particular seam, the seam edges, the
weight of the equipment, the relative labor intensity and the steep slopes of
trench walls are all pontentially troublesome.
Status of the Method: This method is applicable to a quality assurance program
for a hazardous waste disposal facility, especially where the permittee wants
a great degree of confidence in the seam integrity and impermeability. All
the equipment can be purchased for less than $1000. But as it requires a two
man crew and" covers 5 to 6 feet per minute it can be costly in labor costs and
construction time. This method is the best for giving assurance in the seam
integrity of any installed geomembrane. This method will detect leaks the
others will not. This method should be the bottom line, the "last line of
defense," test for any geomembrane usage where impermeability is critical.
Often the labor intensity and time requirements of this method can be
mitigated by using it in conjunction with the air lance method, conductivity
method or an ultrasonic method. These latter three methods can locate larger
anomalies rapidly. Thus the vacuum box will be left only small anomalies
or pinholes to detect and its operation will be more continuous and thus
less costly.
Calibration Procedure: N/A
Documentation of Test: Items to be recorded include leak detections, loca-
tions and markings. No example data sheet is provided.
181
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Method No, 43
Parameter Measured: Geomembrane/Geotextile Seam Integrity
Title of Test Method: Conductivity
Principle of Te'st Method: This method electrically inspects the continuity
of a seam by detecting changes in conductivity.
Test Method
(1) Apparatus: Battery, battery charger, battery tester, ground cable,
coil spring electrodes and power pack.
(2) Procedure: The inspection electrode is passed over the seam. When
anomalies in the seam are detected an audible signal is actuated by the
instrument. The method does not test seam strength.
(3) Reference: Copywright by Tinker & Rasor.
Limitations: This method was developed for high voltage electrical inspec-
tion of pipeline coatings. Changes in the sub-seam soil water content can
cause a change in the soil's dielectric constant and effect the readings.
Thus uniform sub-seam soil nature and water content are desirable for the
conduct of this method.
Status of the Method: This method is applicable to a quality assurance
program for a hazardous waste disposal facility for it will detect seam leaks
as well as bubbles, thin spots or foreign particles. It is relatively
inexpensive and one man can operate it without special training. The high
voltages involved should not present safety problems. Because of its wider
use and acceptance this method was deemed to be currently more applicable
for use at a hazardous waste disposal facility than the similar ultrasonic
method.
Calibration Procedure: The instrument must be ca~" "*••>:• • 'ie conductivit
of the seam beforehand so that only anomalies <
Documentation of Test: Items to be recorded it-~- ictions,
locations and markings. No example data sheet is p.
182
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