c/EPA
United States
Environmental Protection
Agency
Robert S. Kerr Environmental Research
Laboratory
Ada OK 74820
EPA-600/2-79-171b
August 1979
Research and Development
Long-Term Effects of
Land Application of
Domestic
Wastewater
Tooele, Utah,
Slow Rate Site
Volume 2:
Engineering Soil
Properties
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RESEARCH REPORTING SERIES
Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into nine series. These nine broad cate-
gories were established to facilitate further development and application of en-
vironmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The nine series are:
1. Environmental Health Effects Research
2. Environmental Protection Technology
3. Ecological Research
4. Environmental Monitoring
5. Socioeconomic Environmental Studies
6. Scientific and Technical Assessment Reports (STAR)
7. Interagency Energy-Environment Research and Development
8. "Special" Reports
9. Miscellaneous Reports
This report has been assigned to the ENVIRONMENTAL PROTECTION TECH-
NOLOGY series. This series describes research performed to develop and dem-
onstrate instrumentation, equipment, and methodology to repair or prevent en-
vironmental degradation from point and non-point sources of pollution. This work
provides the new or improved technology required for the control and treatment
of pollution sources to meet environmental quality standards.
This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.
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EPA-600/2-79-171b
August 1979
LONG-TERM EFFECTS OF LAND APPLICATION
OF DOMESTIC WASTEWATER: TOOELE, UTAH,
SLOW RATE SITE
Volume II: Engineering Soil Properties
by
Loren R0 Anderson, J. H. Reynolds, R. W. Miller
W. F. Campbell, D. G. Beck, and J. A. Caliendo
Utah Water Research Laboratory
Utah State University
Logan, Utah 84322
Contract No. 68-03-2360
Project Officer
Curtis C. Harlin, Jr.
Wastewater Management Branch
Robert S. Kerr Environmental Research Laboratory
Ada, Oklahoma 74820
ROBERT S. KERR ENVIRONMENTAL RESEARCH LABORATORY
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGENCY
ADA, OKLAHOMA 74820
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DISCLAIMER
This report has been reviewed by the Robert S. Kerr Environmental
Research Laboratory, U. S. Environmental Protection Agency, and approved for
publication. Approval does not signify that the contents necessarily
reflect the views and policies of the U. S. Environmental Protection Agency,
nor does mention of trade names or commercial products constitute endorse-
ment or recommendation for use.
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FOREWO.RD
The Environmental Protection Agency was established to coordinate the
administration of major Federal programs designed to protect the quality
of our environment.
An important part of the agency's effort involves the search for infor-
mation about environmental problems, management techniques, and new technolo-
gies through which optimum use of the nation's land and water resources can
be assured and the threat pollution poses to the welfare of the American
people can be minimized.
EPA's Office of Research and Development conducts this search through
a nationwide network of research facilities. As one of these facilities,
the Robert S. Kerr Environmental Research Laboratory is responsible for
the management of programs including the development and demonstration of
soil and other natural systems for the treatment and management of municipal
wastewaters.
Although land application of municipal wastewaters has been practiced
for years, there has been a growing and widespread interest in this practice
in recent years. The use of land application received major impetus with
the passage of the 1972 amendments to the Federal Water Pollution Control
Act. The 1977 amendments to the Act gave further encouragement to the use
of land application and provided certain incentives for the funding of
these systems through the construction grants program. With the widespread
implementation of land application systems, there is an urgent need for
answers to several major questions. One of these questions regards the
long-term effects of land application on the soil, crops, groundwater, and
other environmental components. This report is one in a series of ten
which document the effects of long-term wastewater application at selected
irrigation and rapid infiltration study sites. These case studies should
provide new insight into the long-term effects of land application of
municipal wastewaters.
This report contributes to the knowledge which is essential for the EPA
to meet the requirements of environmental laws and enforce pollution control
standards which are reasonable, cost effective, and provide adequate
protection for the American public.
William C. Galegar
Director
Robert S. Kerr Environmental Research Laboratory
i i i
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ABSTRACT
A high quality secondary sewage effluent was applied to three soil
types and its effect on the shear strength, consolidation properties, and
permeability of the soils was studied. The three soil types were a poorly
graded sand, a clayey silt, and a highly plastic clay. Each soil was divided
into nine samples. Six samples were leached with secondary sewage effluent
and three with distilled water. Three of the effluent samples were then
re-leached with distilled water in order to investigate the possibility of
any reversible phenomenon.
After a suitable amount of leachate had passed through the samples,
direct shear tests, standard consolidation tests, and falling head permeabi-
lity tests were performed. The shear strengths of the sand and silt were
not appreciably affected by the application of wastewater. The shear
strength of the clay was slightly increased by the wastewater effluent. The
compressibility, rate of consolidation, and permeability of the silt
increased with application of the effluent whereas the clay samples were not
affected by the application. Except for the rate of consolidation at high
stress levels, application of distilled water to treated samples did not
reverse changes in the above properties.
This report was submitted in fulfillment of Contract No. 68-03-2360 by
Utah State University under the partial sponsorship of the U. S. Environmental
Protection Agency, This report covers a period from January 2, 1976, to
June 15, 1978, and work was completed as of December 15, 1978.
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CONTENTS
Foreword . . . . . . . . . . . . iii
Abstract ............ iv
Figures ............ vi
Tables ix
List of Abbreviations and Symbols ....... xi
Acknowledgments . . . . . . . . . . . xii
1. Introduction ......... 1
2. Conclusions 3
3. Recommendations ........ 4
4. Methods 5
General ......... 5
Soil Description ....... 5
Effluent Description 7
Apparatus Descriptions ...... 7
Preparation of Samples and Treatment . . . 11
Tests to Determine Engineering Properties . . 14
5. Results and Discussion ....... 16
Objective 16
Shear Strength . 16
Consolidation Characteristics ..... 43
References ............ 68
Appendices
A. Strain versus effective pressure ..... 70
B. c versus effective pressure for the Smithfield clay
and Tooele silt samples ....... 76
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FIGURES
Number Page
1 Grain size distribution curve for Nibley sand, Tooele silt, and
Smithfield clay 6
2 Disassembled split cylinder used to contain the shear samples 8
3 Cross section of apparatus 9
4 Split cylinder on the loading frame with the water reservoir
bottle and loading yoke in place ...... 9
5 Direct shear apparatus employed in this study . . . . 10
6 Consolidometer used in this study . . . . . . 11
7 Cumulative flow versus time ....... 17
8 Cumulative flow versus time ....... 18
9 Cumulative flow versus time ..... 19
10 Cumulative flow versus time 20
11 Cumulative flow versus time 21
12 Cumulative flow versus time ....... 22
13 Cumulative flow versus time 23
14 Cumulative flow versus time ..... 24
15 Cumulative flow versus time ....... 25
16 Shearing force versus displacement curves for the Tooele silt 32
17 Shearing force versus displacement envelope for the Nibley
sand 33
18 Shearing force versus displacement ...... 34
19 Shearing force versus displacement ...... 35
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FIGURES (Continued)
Number Page
20 Shearing force versus displacement ...... 36
21 Shearing force versus displacement curves, Smithfield clay
distilled water treatment . 37
22 Shearing force versus displacement curves, Smithfield clay,
effluent distilled water treatment 38
23 Shearing force versus displacement, Smithfield clay effluent
treatment ........... 39
24 Peak shearing force versus void ratio for the Nibley sand . 41
25 Tooele silt, cumulative effluent versus time .... 43
26 Tooele silt, sample 4C cumulative water versus time . . 44
27 Tooele silt, sample 5C cumulative water versus time . . 45
28 Tooele silt, sample 6C cumulative water versus time . . 46
29 Tooele silt, cumulative distilled water versus time . . 47
30 Smithfield clay cumulative effluent versus time ... 48
31 Smithfield clay, sample 4 cumulative water versus time . . 49
32 Smithfield clay, sample 5 cumulative water versus time . . 49
33 Smithfield clay, sample 6 cumulative water versus time . . 50
34 Smithfield clay, cumulative distilled water versus time . . 50
35 Dial reading versus time. (Smithfield clay sample # 9C) . 53
36 Smithfield clay, average values of strain and o versus
effective pressure ......... 54
37 Tooele silt, average values of strain and GV versus
effective pressure ......... 55
38 a versus effective pressure for Smithfield clay samples . 59
s
39 a versus effective pressure for Tooele silt samples . . 60
S
40 Hypothetical soil profile for example consolidation problem . 66
vn
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FIGURE (Continued)
Number page
41 Settlement versus time example problem .... 67
A-l Smithfield clay, strain versus effective pressure, effluent . 70
A-2 Smithfield clay, strain versus effective pressure, leached . 71
A-3 Smithfield clay, strain versus effective pressure, distilled
water 72
A-4 Tooele silt, strain versus effective pressure, effluent . . 73
A-5 Tooele silt, strain versus effective pressure, leached . . 74
A-6 Tooele silt, strain versus effective pressure, distilled
water ............ 75
B-l Smithfield clay, c versus effective pressure .... 76
B-2 Tooele silt, o versus log of effective pressure ... 77
vm
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TABLES
Number page
1 Characteristics of the Tooele silt, the Nibley sand, and the
Smithfield clay . . . . . . . . . . 6
2 Quantity of water applied to Smithfield clay samples for direct
shear tests 26
3 Water quality test results for effluents used on the Tooele
silt samples 27
4 Water quality test results for effluents used on the Nibley
sand samples .......... 28
5 Chemical characteristics description of the Tooele silt and
the Nibley sand samples after testing 29
6 Shear test data from the Tooele silt samples .... 30
7 Shear test data from the Nibley sand samples treated for 28
days 30
8 Shear test data from the Smithfield clay samples ... 31
9 Comparison of shear test results for Smithfield clay . . 42
10 Dimensions of Tooele silt samples used in consolidation
and permeability tests 51
11 Dimensions of Smithfield clay samples used in consolidation
and permeability tests ........ 52
12 Slope (c) of the strain vs log of effective stress curve for
Tooele silt 56
13 Slope (C) of the strain vs log of effective stress curve for
Smithfield clay 56
14 Values of the coefficient of consolidation (cy) for Smithfield
clay in (mm2/min) 58
15 Values of the coefficient of consolidation (c ) for Tooele
silt in (mm2/min) 58
ix
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TABLES (Continued)
Number page
16 Values of a for Smithfield clay in (10~3) .... 59
S
17 Values of a for Tooele silt in (10~3) 60
S
18 Permeability (k) for Tooele silt 61
19 Permeability (k) for Smithfield clay ..... 61
20 Results of soil chemistry tests ...... 62
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LIST OF ABBREVIATIONS AND SYMBOLS
LIST OF ABBREVIATIONS
BOD5
Ca
cc
CEC
COD
ESP
ft
I.D.
in.
K
kg
kN
kPa
Ib
m
Mg
mg/£
mm
N
Na
N03N
p
psf
psi
SAR
SS
five day biochemical oxygen VSS
demand
= volatile suspended solids
calcium
cubic centimeters
cation exchange capacity
chemical oxygen demand
exchangeable sodium
percentage
feet
inside diameter
inches
potassium
kilograms
kilonewtons
kiloPascals
pound
meter
magnesium
milligrams per liter
millimeter
Newton
sodium
nitrate nitrogen
phosphorus
pounds per square foot
pounds per square inch
sodium adsorption ratio
suspended solids
SYMBOLS
c
v
Cc
eo
HDP
k
LL
PI
t
t5 0
V
Vv
ct(0.10)
as
£
a
= Slope of the e-log a curves
= Coefficient of consolidation
= Compression index
= Initial void ratio
= Length of the longest
drainage path of a sample
= Coefficient of permeability
= Liquid Limit
= Plastic Index
= Time
= Time at 50 percent
consolidation
= Total volume of sample
= Volume of voids
= 10 percent significance
level
= Rate of secondary
consolidation
= Strain
= Intergranular or effective
stress
= Friction angle
XI
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ACKNOWLEDGMENTS
Mr. Rene Winward, of the Utah State University Civil Engineering
Department, manufactured most of the equipment used in this study. His
skills and helpful suggestions are greatly appreciated. Acknowledgment
and thanks are also extended to Dr. Donald V. Sisson, of the USU Applied
Statistics Department, for his assistance with the statistical analysis.
This work was performed under a U. S. Environmental Protection Agency
Contract Number 68-03-2360. The support of the Robert S. Kerr Environmental
Research Laboratory is greatly appreciated, especially the direction of
Dr. Curtis C. Harlin, Jr., who served as the EPA Project Officer.
xn
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SECTION 1
INTRODUCTION
Present methods of discharging treated and untreated domestic wastes
have exceeded the capacity of many receiving streams. The resulting
pollution poses a threat to the usable water supply. Controlled land
application of these wastewaters has potential as a means of reducing the
load on the present surface water supplies. If the wastewater is used for
agricultural purposes, it promotes the growth of plants, provides economical
treatment of wastewater, conserves water and nutrients normally wasted and
thereby makes more freshwater available for domestic use.
An understanding of the effects of domestic wastewater on the physical
engineering properties of soil could be very important for land use planning
of existing and potential land disposal sites. Consideration must be given
to the effects on the physical engineering properties of the soil not only
during the period of application of effluent to the site, but also to the
long-term effects after the site is no longer receiving the effluent.
The effects on the permeability of a soil from wastewater application
has been investigated by a number of researchers. De Vries [1972], Allison
[1947], Day, et al. [1972], Lanoe and Whisler [1972], and Rice [1974] all
reported a decrease in permeability from wastewater treatment. Various
reasons were suggested: pore clogging from biological activity [Allison,
1947], impermeable surface mat formation [de Vries, 1972], insoluble gas
blocking the pores \_Lanoe and Whisler, 1972; Rice, 1974], and deterioration
of the surface soil structure [Day., et al. , 1972].
The nature of the adsorbed cations has been shown to influence the
engineering properties of soils. Shairiberg and Caiserman [1971], Mitchell
[1976], and Olsen and Mesri [1970] suggested that adsorbed ions of a higher
valence create a more permeable soil than lower valence ions. Aziz, et al.
[1966] indicated that a loss in shear strength occurs with an increase in
exchangeable sodium percentage. Mesri and Olsen [1971] showed the influence
of the electrolyte concentration on the compressibility of montmorillonite
clays.
The existence of large amounts of organic matter in soil is generally
not desirable from an engineering standpoint. This organic material may
cause high plasticity, low permeability and low strength. Also an increase
in the amount of organic matter causes an increase in the optimum water
content for compaction. This leads to a reduction in the maximum unconfined
compressive strength [Mitchell, 1976]. Anders land and Matthew [1973] made a
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study on papermill sludges consisting mainly, of kaolinite clay and found
that the compression index, C0, increased linearly with an increased organic
content.
The purpose of this study was to investigate the influence of the
application of secondary wastewater effluent on the engineering properties
of soil. The specific effects on compressibility, consolidation, and shear
strength of three different soils were studied.
The study was carried out in the laboratory on samples of sand, silt,
and clay. Nine remolded samples of each soil were prepared for each test.
The nine samples were divided into three groups and subjected to treatments
that represented a base line condition, a condition during and immediately
after application of secondary wastewater effluent, and a long-term condition
after application of wastewater had stopped and fresh water had been allowed
to leach through the soil.
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SECTION 2
CONCLUSIONS
This study investigated the effects of a high quality secondary waste-
water effluent on the engineering properties of three different soils. The
soils used in this study were classified by the Unified Soil Classification
System as a poorly graded sand (SP), an inorganic clayey silt to silty clay
(CL-ML), and an inorganic clay of high plasticity (CH). Based on the
results of this study the following conclusions can be made.
1. The shear strength of samples of sand prepared to a relative density
near 100 percent was not affected by leaching the samples with secondary
wastewater effluent.
2. The shear strength of normally consolidated samples of clayey silt to
silty clay was not affected by leaching the samples with secondary
wastewater effluent.
3. The shear strength of normally consolidated samples of a highly plastic
clay was slightly increased by the application of a secondary waste-
water effluent. The change in shear strength did not reverse after
application of distilled water to the treated samples.
4. The compression index, c, of normally consolidated samples of clayey
silt to silty clay soil increased with application of the secondary
wastewater effluent. This increase in compressibility did not reverse
when treated samples were leached with distilled water.
5. At high stress levels, the coefficient of consolidation, cy, of normally
consolidated samples of clayey silt to silty clay soil increased with
application of the secondary wastewater effluent. Application of
distilled water to treated samples caused a reverse in the process at
high stress levels.
6. The secondary consolidation characteristics of normally consolidated
samples of clayey silt to silty clay were not affected by application
of the secondary wastewater effluent.
7. The consolidation characteristics of normally consolidated samples of
the highly plastic clay were not affected by application of the
secondary wastewater effluent.
8. The coefficient of permeability of normally consolidated samples of the
clayey silt to silty clay increased with application of the effluent.
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SECTION 3
RECOMMENDATIONS
Further research is recommended to more clearly define the effect of
wastewater effluent on the engineering properties of soil. Of particular
concern would be the following.
1. Using a wastewater effluent of much poorer quality to treat the samples
(primary treatment only).
2. Using a clay soil with a much lower exchangeable sodium percentage (ESP)
than the 54.8 used in this study.
3. Using samples of sand prepared to a relative density less than 50
percent.
4. Separating the chemical and biological effects on the engineering
properties.
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SECTION
METHODS
GENERAL
A laboratory study was conducted to evaluate changes in engineering
soil properties from applying domestic wastewater to the soil and to
determine if these changes were irreversible. The methodology involved
applying three different treatment combinations of sewage and/or distilled
water to three different soil types (sand, silt, and clay) and then testing
each group for various engineering properties. The main properties
investigated were consolidation, permeability, and shear strength.
Each soil type was initially divided into nine samples and soaked in
distilled water to achieve saturation. After the initial soaking period
(which varied depending on soil type), the soil was carefully placed in
the appropriate testing apparatus for treatment and laboratory testing. One
of three different treatments was used on samples of each soil type:
Leaching the soil with distilled water and then performing the tests.
Leaching the soil with sewage and then performing the tests.
Leaching the soil first with sewage followed by distilled water and
then performing the tests.
Three replications of each test were used in each group and the results
were averaged. To avoid the effects of sample disturbance, the samples were
prepared, treated and tested in the same container. To accomplish this it
was necessary to design and fabricate nearly all of the testing equipment.
The samples were prepared, treated, and tested under the same general
environmental conditions in a constant temperature room.
SOIL DESCRIPTION
The names referring to the soils used in the laboratory study were
chosen for convenience only and have no relation to the United States
Department of Agriculture soil survey names. Atterberg Limits, specific
gravity, and a grain size analysis were run on each soil type in accordance
with ASTM specifications. Table 1 shows the results of these tests.
The Nibley sand was obtained in Nibley, Utah, from stockpiles at the
wash plant of a local concrete producer. The absence of any clay size
particles in this sand is due to the washing process the sand went through
before the samples were obtained. The textural classification system used
by the U.S. Department of Agriculture designates the soil as a sand. Using
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TABLE 1. CHARACTERISTICS OF THE TOOELE SILT, THE NIBLEY SAND, AND THE
SMITHFIELD CLAY
Soil Type Atterberg Limits
Nibley Sand
Tooele Silt
Smithfield Clay
LL
N.P.*
25
59
PI
N.P.
4
38
Specific
Gravity
2.73
2.62
2.72
Composition
% Sand
96
34
4
% Silt
4
53
54
% Clay
0
13
42
Cation
Exchange
Capacity
(me/100 g)
1.5
15.1
22.8
* N.P. = Non Plastic
the Unified Soil Classification System, the soil is classed as SP.
size distribution curve for this soil is shown in Figure 1.
A grain
The Tooele silt was taken from near the surface in fields directly north
of the Tooele Army Depot in Tooele, Utah. Based on the USDA textural
classification, the Tooele silt is classified as a silt loam. According to
the Unified Soil Classification System, the Tooele silt possesses character-
istics of two groups and is designated by the combination of both group
symbols as CL-ML. A grain size distribution curve for this soil is shown in
Figure 1.
100
80-
m 60H
a:
LJ
40-
20^
Smithfield clay
1.0 0.5 O.Z 0.1 0.05 0.02 0.01 0.005 0.002 0.001
DIAMETER (mm)
Figure 1. Grain size distribution curve for Nibley sand, Tooele
silt, and Smithfield clay.
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The Smith-field clay was obtained from a location northwest of Smithfield,
Utah. The USDA textural classification designates the soil as clay. By the
Unified Soil Classification System, Smithfield clay has the group symbol CH
and is described as an inorganic clay of high plasticity. A grain size
distribution curve for this soils is shown in Figure 1.
EFFLUENT DESCRIPTION
The treated wastewater effluent used for the laboratory study was
obtained from the Preston, Idaho, sewage treatment plant located 40 km
(25 miles) north of Logan. This facility serves the City of Preston which
has a population of approximately 3,300. The facility has a design capacity
of 7500 m3/day (two mgd). The plant employs primary and secondary treatment.
The secondary treatment consists of a standard trickling filter and anaero-
bic digestor. Final settling is followed by chlorination to a chlorine
residual of 2.0 mg/£.
Effluent was collected at the treatment plant by placing a container
in the effluent from the chlorine contact chamber. The chemical composition
of the effluent was determined according to Standard Methods [APHA, 1976] at
the beginning and end of each application period. The suspended solids
concentration ranged from 7 to 15 mg/£ and the biochemical oxygen demand
(BODs) concentration ranged from 7 to 30 mg/£.
APPARATUS DESCRIPTION
General
Special equipment was designed and fabricated for both the shear tests
and consolidation tests. Falling head permeability tests were run on the
consolidation samples at the end of the last loading increment. The shear
strength was measured in a direct shear apparatus on 101.6 mm (4 in.)
diameter double drained consolidometers. The apparatus for both the direct
shear samples and consolidation samples were equipped so that the specific
treatments could be leached up through the soil from the bottom to the top.
Direct Shear Apparatus
The equipment required for the laboratory study of shear strength
included the following: split cylinders, filter stones, loading yokes,
weights, loading frame, water reservoirs, and a direct shear machine. Some
of this equipment could be purchased commercially but much of it had to be
designed and constructed specifically for the needs of this study.
The split cylinder shown in Figure 2 was used to contain the sample.
This allowed all the loading, treatment, and testing of the sample to be
done in a single container and thus, minimized sample disturbance in
transferring the sample from the loading frame to the direct shear apparatus.
The split cylinders were constructed of clear acrylic tubing having an
outside diameter of 127.0 mm (5 in.) and a wall thickness of 12.7 mm (0.5
in.). Each cylinder consisted of two separate parts. The lower half was
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Figure 2. Disassembled split cylinder used to contain the shear samples.
76.2 mm (3 in.) high and the upper half was 88.9 mm (3.5 in.) high. The two
sections were connected together by stainless steel bolts which passed
through holes in the upper half and were threaded into the lower half. These
bolts were removed during testing. When the cylinders were assembled, a
thin coating of petroleum jelly was applied to the two contact surfaces.
This not only provided a watertight seal at that joint, but also helped to
reduce the friction between the upper and lower halves of the plastic
cylinder when the samples were sheared. The bottom plate in the lower half
of the cylinder, shown in the apparatus cross section in Figure 3, was made
from 12.7 mm (0.5 in.) thick clear plexiglass. Two concentric circular and
eight radial grooves were cut into the plate on the inside surface to
provide a more even distribution of the water entering the sample through
the bottom plate.
Two corundum stones of medium porosity were used in each cylinder. The
stones were 6.35 mm (0.25 in.) thick and 101.6 mm (4 in.) in diameter. One
stone was inserted directly over the bottom plate of the shear cylinder and
the other was placed on top of the soil surface after the sample was in place.
A loading disc of 12.7 mm (0.5 in.) thick plexiglass was placed above the
upper stone. In the center of the loading disc was a concave seat to aid in
the proper positioning of the loading yoke.
The loading yoke, shown in Figure 4, transferred the load from the
weights to a normal load acting on the top of the soil sample. Two different
sizes of steel weights, 4 kg mass (8.82 Ibs) and 5 kg mass (11.03 Ibs), were
used in varying combinations to obtain the three different normal pressures
of approximately 20.7 kPa (3 psi), 41.4 kPa (6 psi), and 62.1 kPa (9 psi).
A reservoir for each sample was provided by 250 m£ glass bottles as
-------
VD
\
V
0,5"
2.!
3.(
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10*
in" -
C.U
E
E
«-nu
o.U
D
^EJW
' ^
G
WMfUMSMtPBCPgafa
-Hoi
i
D
D.5" H'u (5.5
on"
^l.65ILj
Irl.O
±025"
Tos"
A Porous stone
B -- Loading disc
C -- Bottom plate
D -- Shear cylinder walls
E Shear blocks
F -- Shear plane
G -- Soil sample
N -- Normal force
S -- Shearing force
Figure 3. Cross section of apparatus,
Figure 4. Split cylinder on the loading frame with
the water reservoir bottle and loading
yoke in place.
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shown in Figure 4. A piece of flexible tygon tubing connected the reservoir
bottles to a brass fitting in the bottom of the split cylinder. By raising
the bottle above the elevation of the soil in the shear cylinder, a hydraulic
head was provided and the water in the bottle flowed up through the sample.
The direct shear apparatus is shown in Figure 5. The upper half of the
direct shear apparatus moved freely on ball bearings located between the two
sections. The split cylinder fit snugly into the shear box. The horizontal
split between the two halves of the split cylinder matched exactly with the
juncture between the box sections. The soil sample in the split cylinder
was subjected to a constant normal load while an increasing horizontal
force was applied to the upper section of the shear box. After the three
bolts connecting the two halves of the split cylinder were removed, the
applied horizontal force caused the soil sample to shear along the juncture
between the shear box sections. Loading for the horizontal shearing force
was by means of a hand crank operating through a gear system. A proving
ring was used to measure the horizontal load applied to the sample. The
shear displacement was measured with a dial indicator.
Figure 5. Direct shear apparatus employed in this study.
Consolidation Apparatus
The equipment used in the consolidation phase of this study consisted
of a standard consolidation test loading frame, nine double drained
consolidometers, loading yokes for each consolidometer, a sample treatment
loading frame and a falling head permeability apparatus.
A standard consolidation test loading frame manufactured by Soiltest,
Inc. was used during the consolidation tests on each sample. Three bays of
10
-------
the loading frame were used simultaneously in order to accommodate the
three replications of each specific treatment.
The consolidometers shown in Figure 6 were about 95.25 mm (3.75 in.)
high and were fabricated from 114.3 mm (4.5 in.) I.D. aluminum pipe of 6.35
mm (0.25 in.) wall thickness. The aluminum was lined with 6.35 mm (0.25 in.
thick plexiglass tubing, to provide smooth walls, and a plexiglass disc
formed the bottom. Corundum stones were used at the top and bottom of the
sample to provide double drainage of the sample. Prior to placing soil in
the consolidometers, the sides were lightly coated with Vaseline to reduce
wall friction during testing.
Figure 6. Consolidometer used in this study.
A special loading yoke and frame, similar to that for the direct
shear samples shown in Figure 4, were used to consolidate the samples under
an initial vertical pressure of 13.3 kPa (278 lb/ft2) and to maintain the
load during application of the specific treatment required for each sample.
Distilled water and/or wastewater effluent were stored in 250 m£ bottles
mounted on the loading frame and connected to the bottom of the samples with
a polyethylene tube. The bottles were positioned on the frame to maintain
an elevation head of about 0.61 m (2 ft) above the top of the samples.
PREPARATION OF SAMPLES AND TREATMENT
General
Samples of Nibley sand, Tooele silt, and Smithfield clay were prepared
in a manner to achieve identical initial conditions prior to application of
the three different treatments. Essentially the same procedure was used to
11
-------
prepare the Tooele silt samples and the Smithfield clay samples except that
the clay was initially dried and pulverized and the soaking period was
longer for the clay. A slightly different procedure was used to prepare the
Nibley sand. Only direct shear tests were run on the Nibley sand.
Preparation of the Nibley Sand Sample?
Preparation of the Nibley sand started by retaining only that portion
passing a #16 (1.18 mm) sieve. Nine samples of approximately equal volume
were obtained by systematically passing the soil through a sample splitter.
The direct shear test split cylinders were then assembled and a porous stone
was placed in the bottom of each cylinder. To maintain a close uniformity
among the samples, the soil in each cylinder was compacted to approximately
the same density. To do this, the initial volume and weight of each cylinder
was carefully measured and recorded. The air dried sand was poured into the
cylinders through a small funnel. A low distance of fall for the soil of
0.50 mm (0.2 in.) and rotating the funnel in a circular pattern over the
inside area of the cylinder helped to avoid particle segregation when filling
the cylinders with the sand. The cylinder was then placed on a pneumatically
powered vibrating table to densify the sand. After densification, volume
and weight measurements were again taken and the density of the soil in the
cylinder was calculated. The densities of the nine samples ranged between
17.13 _ 17.44 kN/m3 (109 - 111 lbs/ft3).
The upper porous stone and the plastic loading disc were placed on top
of the sample and a normal load of approximately 41 kPa (6 psi) was applied
to each of the nine samples.
To saturate the samples, flexible polyethylene tubing was connected to
the brass fitting in the bottom of each split cylinder and extended up along-
side the cylinder. Distilled water was applied through this tube under a
head of only a few inches until the sample was completely saturated and
water was ponded above the plastic loading disc.
Preparation of the Tooele Silt and
Smithfield Clay Samples
Preparation of the Tooele silt and Smithfield clay samples began by
screening the soil. Only the material passing the #40 (0.425 mm) sieve was
used. This material was obtained using a 20 cm (8 in.) round brass sieve
on a mechanical shaker. To secure a uniform sample, the soil was stirred
and mixed by hand to eliminate any segregation that may have occurred during
the sieving process. To further insure uniformity among the samples, all
the material was repeatedly passed through a sample splitter and broken
down into 10 equal samples. Distilled water, which had been boiled under a
vacuum, was added to each of the 10 samples. The soil and water were care-
fully mixed into a slurry with the consistency slightly less than that at
the liquid limit. The slurry was then submerged in the distilled water and
placed in a constant temperature room. Frequently a large knife was used to
slowly slice through the sample to allow any air bubbles that may have been
trapped to escape. The Tooele silt samples were allowed to soak in this
manner for 10 weeks to assure complete saturation, and the Smithfield clay
12
-------
samples were soaked for approximately 6 months.
When the soaking period was completed, the samples were placed in the
shear and consolidometer cylinders. The cylinders were connected and filled
approximately one-fourth full of distilled water. The bottom porous stone,
which had been soaked in distilled water, was placed at the bottom of the
cylinders. The soil was scooped out of the soaking container by large
spoonfuls and placed into the water in the cylinders. Care was taken to
avoid inducing any air bubbles as each spoonful was slowly submerged in the
water. When the soil had filled the cylinders to the desired depth, the
upper porous stone was placed directly on top of the soil. The plastic
loading disc was then set on top of the upper porous stone and the samples
were loaded with an initial seating load of approximately 41.4 kPa (6 psi).
The normal load was added in small increments until the desired load was on
the sample. After the samples had consolidated under the applied normal
seating load, the various treatments were applied to the samples.
The permeability of the Smithfield clay was much lower than that of the
Tooele silt and so a thinner sample was used for both the shear tests and
consolidation tests. This enabled the various treatments to be applied to
the soil in a reasonable length of time.
Treatment Methods
The soil properties of the Tooele silt, the Smithfield clay, and the
Nibley sand were very different, as would be expected. Because of this, a
different method of applying the water to each soil type was used.
The permeability of the Tooele silt and Smithfield clay were both rather
low. Therefore, a continuous flow was maintained through the samples. As
the water flowed up through the samples, the head varied between 0.483 and
0.406 m (19 and 16 in.). To maintain a somewhat consistent quality of water
being leached through the sample, the water was changed at intervals of 3 to
4 days. The 250 m£ reservoir bottles had sufficient volume to supply all
the water that would permeate through the sample during this period.
The sides of the reservoir bottles were calibrated and the volume of
water passing through the sample in any given period of time was determined.
The water level in each reservoir bottle was read to the nearest 5 mH and
recorded daily to determine the flow through the soil sample.
The Nibley sand was much more permeable than the Tooele silt and
Smithfield clay. Water would flow through the samples very easily under a
head of less than 25 mm (1 in.). Because of these conditions, it was not
practical to maintain a continuous flow through the sand samples. Instead,
at intervals of 3 to 4 days, approximately 500 m£ of water was placed in
the reservoir bottles and allowed to flow through the sample. As the
displaced water exited from the top of the sample, it was drained off. The
hydraulic head during the flow of water through the soil varied from 0 cm
(0 in.) to 25.4 cm (10 in.). During the days between treatments, water was
intermittently added to the top of the sample to overcome the effects of
13
-------
evaporation and to maintain the sample in a saturated condition.
Types of Treatment
Treatment of the soil samples was divided into three different groups.
Each group was representative of a different condition in the field. One
group received only distilled water during the leaching process. This
represented and established the engineering properties of the soil prior to
land disposal of the treated effluent. The second group received only
sewage treatment plant effluent for the entire length of the leaching period
This represented the soil during land disposal of the treated effluent and
the test results on these samples indicated whether the treated effluent had
any effect on the engineering properties of the soil. The third group of
samples received a third type of treatment. These samples having first
received sewage treatment plant effluent for a period of time, were leached
with distilled water for the remainder of the leaching process. This
attempted to establish the long-term engineering properties of the soil and
to indicate whether changes in the properties as a result of receiving
treated effluent were reversible.
TESTS TO DETERMINE ENGINEERING PROPERTIES
Direct Shear Tests
When a direct shear test was to be performed, the weights were removed
from the loading yoke and the yoke was taken off the sample. The split
cylinder, with the tubing still attached, was then removed from the loading
frame and carefully placed into the shear box of the direct shear apparatus.
The loading yoke was put back on the sample and the same weights were
replaced. The hand crank was turned just enough to make contact with the
proving ring. Both the dial indicator on the proving ring and the one used
to measure displacement were zeroed. The three bolts connecting the two
halves of the split cylinder were removed.
To apply the shearing force, the hand crank was turned at the rate of
six revolutions per minute. This produced a strain rate, based upon the
diameter of the soil sample, of 2 percent per minute. Readings from both
dial indicators were recorded at 10 second intervals. Testing was continued
until the total strain was over 20 percent. The split cylinder was then
removed from the shear box. The soil samples from one-third of the tests on
the Tooele silt were dried in the oven and the water content and void ratio
were calculated. The remaining two-thirds of the Tooele silt samples were
frozen and stored until a chemical composition analysis could be performed
on them to identify any differences caused by the different treatments.
Only two of the Nibley sand samples were saved and chemical composition
analysis was performed on them.
Consolidation Tests
Standard consolidation tests were performed on both soil types for all
three treatments. After enough distilled water or sewage effluent had
14
-------
passed through the samples to replace the pore water, the consolidometers
were placed in the standard consolidation loading frame. The samples were
allowed to consolidate under the initial pressure of 13.17 kPa (275 psf) for
approximately 24 hours before the actual consolidation tests were started.
Consolidation pressures of approximately 19.6 kPa (410 psf), 39.2 kPa (820
psf), 78.5 kPa (1640 psf), 156 kPa (3260 psf), and 1312 kPa (6520 psf) were
used. The duration of each load increment was approximately 48 hours. Two
rebound points were determined for each sample. These points typically
corresponded with consolidating pressures of approximately 78.5 kPa (1640
psf) and 19.6 kPa (410 psf). The samples were allowed to rebound under
each pressure for approximately 24 hours before a dial reading was recorded.
Permeability Tests
Permeability tests were performed on the consolidation samples. Once
the final rebound had occurred and the dial reading had been recorded, the
consolidation samples were subjected to a falling head permeability test.
The 19.6 kPa (410 psf) load was left in place on the sample during the
permeability test. The permeability apparatus described earlier was filled
with distilled water and connected to the consolidometers. Head loss versus
time was recorded.
Permeability tests were not performed on the clay samples 1, 2, and 3.
These samples were subjected to sewage effluent and it was felt that by
adding distilled water to the system, the cation exchange properties might
be altered.
15
-------
SECTION 5
RESULTS AND DISCUSSION
OBJECTIVE
The principal purpose of this study was to investigate whether or not
the effect of chemical and biological activity in the porewater of soil
caused by the application of secondary treated effluent for an extended
period of time changes the principal engineering properties of the soil; and
if so, are the changes reversible upon leaching freshwater through the soil.
SHEAR STRENGTH
General
The results of all the shear tests performed on the sand and silt
samples indicated that the shear strength was not appreciably affected by
the application of the sewage treatment plant effluent. A slight increase
in the shear strength of the clay was observed.
Quantity of Water Added to Samples
The total volume of distilled water and treated sewage effluent applied
to each sample of Tooele silt is shown in Figures 7 through 15. The volume
varied from a minimum of 155 m£ to a maximum of 810 m£ and averaged about
450 m£. The time periods over which the applications took place were 30
and 56 days. The wide variation in the total volume applied to each sample
was partially due to the formation of an insoluble gas in some of the samples
being treated with sewage effluent, which accumulated and blocked the flow
of water through the sample. Frequently, this gas was bled off by momentarily
disconnecting the tubing from the bottom of the split cylinder.
The same amount of distilled water or treated sewage effluent was
applied to each of the Nibley sand samples during the 28 day treatment
period. This volume was 4750 mSL.
The total volume of distilled water and treated sewage effluent applied
to each sample of Smithfield clay is shown in Table 2. Since the permeability
of the clay was very low, a much thinner sample was used. The time period
over which the application of the various treatments took place was 92 days.
Three samples were leached with distilled water for the full 92 days and three
samples were leached with sewage effluent for the full 92 days. The third
set of three clay samples was leached with sewage effluent for the first 63
days and then leached with distilled water for the remaining 27 days.
16
-------
lOOOi
600-
o
UL
> 400
<
200
o
0
0
Tooele Silt
Normal load - 123.42 Ibs
Distilled water
10
20 30 40
TIME (days)
50
60
Figure 7. Cumulative flow versus time.
-------
CO
1000
_800-
1
§600J
LU
^400-
o
200-
Tooele Silt
Normal load - 82.15 Ibs
Distilled water
10
20 30 40
TIME (days)
50 60
Figure 8. Cumulative flow versus time.
-------
lOOOi
800-
o 600-
UJ
£: 400
o
200
Tooele Silt
Normal load - 44.45 Ibs
Distilled water
10
20 30 40
TIME (days)
50 60
Figure 9. Cumulative flow versus time.
-------
1000
ro
O
800-
I 600-
U.
UJ
^ 400-
o
200-
Tooele Silt
Normal load - 123.23 Ibs
Effluent
Head increased at 30 days
from 18" to 36"
10
20 30 40
TIME (days)
50 60
Figure 10. Cumulative flow versus time.
-------
IX)
lOOCh
800-
3
U.
600-
UJ
^400
o
200
0
0
Tooele Silt #5S
Normal load- 82.01 Ibs
Effluent
10
20 30 40
TIME (days)
50 60
Figure 11. Cumulative flow versus time.
-------
lOOOi
800^
600
p4001
8 20CH
0
6
Tooele Silt
Normal load - 44.39 Ibs
Effluent
10
20 30 40
TIME (days)
50 60
Figure 12. Cumulative flow versus time.
-------
ro
CO
lOOOi
800-
600
UJ
~ 400
200
o
0
Tooele Silt #7S
Normal load - 82.73 Jbs
Effluent
Head Increased at 30 days
from 18" to 36"
10
20 30 40
TIME (days)
50
60
Figure 13. Cumulative flow versus time.
-------
1000-
800
600-
LJ
^ 400H
5
200-
Tooele Silt#8S
Normal load - 123.40 Ibs
Effluent
10
20 30 40
TIME (days)
50 60
Figure 14. Cumulative flow versus time.
-------
ro
en
lOOOi
800J
g 600-
_j
u_
UJ
400
3200
0
0
Tooele Silt
Normal load- 44.41 Ibs
Effluent
Head increased at 30 days
from 18" to 36"
10
20 30 40 50 60
TIME (days)
Figure 15. Cumulative flow versus time.
-------
TABLE 2. QUANTITY OF WATER APPLIED TO SMITHFIELD CLAY SAMPLES FOR DIRECT
SHEAR TESTS
Sample
1
2
3
4
5
6
7
8
9
Treatment
Distilled
water
only
Effluent followed
by distilled
water
Effluent only
Time
(days)
92
92
92
92
92
92
92
92
92
Accumulated
Distilled Water
(mi)
380
435
365
90
105
no
_
-
-
Volume of
Effluent
(m£)
_
-
-
205
220
260
335
350
335
Quality of Water Added to Samples
The results of the water quality analysis of the sewage treatment plant
effluent samples indicate that the effluent was of high quality. The
composition of the distilled water and the effluent applied to both the
Tooele silt and the Nibley sand samples is shown in Tables 3 and 4. The
effluent used to treat the Smithfield clay samples was obtained from the
same point in the treatment process and generally at about the same time
of day.
Chemical Description of Soils
A chemical characteristic description for both kinds of soil samples
treated with effluent and for those treated with distilled water is shown
in Table 5. The soil tests performed showed no appreciable differences among
the samples of each kind of soil in the water soluble salts, the total
extractable cations, and the cation exchange capacity. Tests were not
performed on the Smithfield clay samples used for the shear tests. However,
the soil and treatment procedures were the same for the shear test samples
as for the consolidation samples. The chemical characteristics of the
Smithfield clay consolidation samples is given in Table 20.
Direct Shear Test Results
c ear es esus
Test results for the Tooele silt, the Nibley sand and the Smithfield
samples are shown in Tables 6, 7, and 8. Shearing force versus
lacement curves for the Tooele silt samples are shown in Figure 16. A
ring force versus displacement envelope for the Nibley sand samples is
26
-------
TABLE 3. WATER QUALITY TEST RESULTS FOR EFFLUENTS USED ON THE TOOELE SILT SAMPLES
Day #
0
3
7
14
17
Sample
Type
Distilled Water
Old Effluent
Fresh Effluent
Average
Distilled Water
Old Effluent
Fresh Effluent
Average
Distilled Water
Old Effluent
Fresh Effluent
Average
Distilled Water
Old Effluent
Fresh Effluent
Average
Distilled Water
Old Effluent
Fresh Effluent
Average
N03-N
pH mg/£
as
Nitrogen
5.62 --
_
7.30 4.19
7.30 4.19
6.35 --
7.18 3.66
7.41 6.50
7.30 5.08
4.45 --
7.55 6.37
7.28 9.19
7.42 7.78
6.48 --
7.19 5.95
7.32 6.28
7.26 6.12
7.19 --
8.55 7.39
8.26 4.93
8.41 6.16
Ca++
--
-»
82.8
82.8
78.2
94.5
86.4
0.88
98.5
68.5
83.5
--
87.7
88.2
88.0
--
78.8
81.1
80.0
Mg++
__
__
11.2
11.2
--
17.2
14.3
15.8
--
8.2
21.0
14.6
--
11.0
8.7
9.9
--
15.3
25.0
20.2
mg/£
Na+
--
__
38
38
--
39
105
72
--
105
43
74
--
48
43
45.5
43
150
96.5
K+
--
7.3
7.3
--
7.2
8.0
7.6
--
8.0
7.3
7.7
--
7.3
7.5
7.4
7.6
7.8
7.7
Total P
--
_ _
4.13
4.13
--
3.23
3.76
3.50
--
3.98
3.71
3.85
--
4.38
4.24
4.31
--
4.11
4.32
4.22
SS
--
10.6
10.6
--
14.4
10.3
12.4
11.0
19.6
15.3
--
9.6
12.8
11.2
--
--
--
vss
--
--
--
--
10.2
7.2
8.7
--
8.3
13.0
10.7
--
7.0
8.8
7.9
--
--
--
mg/£
BOD5
--
--
--
--
9.0
6.0
7.5
--
__
--
--
10.0
8.8
9.0
--
12.0
9.0
10.5
COD
--
--
--
--
--
46.0
43.7
44.9
--
42.2
48.3
45.3
--
36.7
44.7
40.7
ro
(continued)
-------
TABLE 3 (continued)
Day
21
24
# Sample
Type
Distilled Water
Old Effluent
Fresh Effluent
Average
Distilled Water
Old Effluent
Fresh Effluent
Average
6
7
7
7
7
7
PH
.21
.58
.35
.47
.21
--
.21
N03-N
mg/£
as
Nitrogen
--
1.51
6.44
3.98
--
6.22
6.22
Ca
--
93.7
82.3
88.0
--
94.7
--
94.7
-1-4.
Mg
15.5
15.6
15.6
0
--
0
mg/&
+
Na
--
150
46
98
--
48
--
48
+
K
--
7.8
6.9
7.3
--
7.0
--
7.0
Total P
-
4.
3.
4.
-
3.
-
3.
-
62
88
25
-
75
-
75
mgA
SS VSS BOD5 COD
__
37.3
44.3
40.8
__
__ ____ __
__
ro
CO
TABLE 4. WATER QUALITY TEST RESULTS FOR EFFLUENTS USED ON THE NIBLEY SAND SAMPLES
Day
0
7
# Sample
Type
Distilled Water
Old Effluent
Fresh Effluent
Average
Distilled Water
Old Effluent
Fresh Effluent
PH
5.9
7.6
7.6
5.8
7.6
7.6
N03-N
mg/£
as
Nitrogen
2.14
2.14
--
1.53
2.17
Ca++
84.2
84.2
--
63.8
89.7
mg/£
Mg++ Na+ K+ Total P
60 7.1
60 7.1
__
2.2 -- -- 7.73
8.5 - 9.80
mg/£
SS VSS BOD5
__
-_
-_
8.52 7.21 3.6
5.92 3.67 3.9
COD
__
--
--
--
39.5
52.5
(continued)
-------
TABLE 4 (Continued)
Day # Sample
Type
Average
14 Distilled Water
Old Effluent
Fresh Effluent
Average
21 Distilled Water
Old Effluent
Fresh Effluent
Average
28 Distilled Water
Old Effluent
Fresh Effluent
Average
N03-N
PH m9f
Nitrogen
7.6 1.85
6.1
7.3 --
7.6 2.38
7.5 2.38
5.8 --
8.0 1.98
8.0 2.34
8.0 2.66
5.6 --
7.7 --
7.7 --
7.7 --
Ca++
76.8
--
104.1
77.1
90.6
--
87.6
79.3
83.7
--
72.1
66.1
69.1
mg/£
Mg++ Na+
5.4
--
-- 98
-- 104
-- 101
5.4 105
5.6 88
5.5 96.5
__
10.8 69
12.1 68
11.5 68.5
mg/£
K+ Total P SS VSS BOD5 COD
8.77 7.22 5.44 3.8 46.0
__
8.1 4.00 5.56 4.67 21.8 54.3
8.1 4.16 10.83 10.56 37.6 60.5
8.1 4.08 8.20 7.62 29.7 57.4
__
7.8 3.56 4.58 3.13 7.5 35.6
8.0 4.94 16.14 12.95 26.3 91.1
7.9 4.25 10.36 8.04 16.9 63.4
__
7.2 3.41 20.28 19.72 21.6 42.4
7.9 4.28 16.29 12.86 37.5 91.4
7.55 3.85 18.29 16.29 29.6 66.9
ro
TABLE 5. CHEMICAL CHARACTERISTICS DESCRIPTION
TESTING
Soil Type
Tooele Silt
Nibley Sand
Treatment
Type
Distilled
Water
Effluent
Distilled
Water
Effluent
Sample
Number
2
3
4
6
8
9
1
4
OF
THE TOOELE
H20 - Solubility
(me/lOOg)
Ca
0.2
0.2
0.2
0.2
0.1
0.2
0
0
Mg
0.
0.
0.
0.
0.
0.
0
0
Na
0
0
0.1
0.1
0.1
0.1
0
0.1
K
0
0
0
0
0
0
0
0
SILT
AND THE NIBLEY SAND SAMPLES AFTER
NH»OAC extract
-(me/100g)
Ca
39
40
38
38
36
36
24
21
Mg
3.7
3.8
3.5
3.8
3.5
3.4
0.8
0.7
Na
0.4
0.4
0.4
0.5
0.4
0.5
0.2
0.3
K
0.6
0.6
0.6
0.6
0.5
0.5
0
0
Cation Exchange
Capacity
(me/lOOg)
14.2
16.0
11.2
14.6
15.3
18.5
1.5
1.5
-------
TABLE 6. SHEAR TEST DATA FROM THE TOOELE SILT SAMPLES
Sample
Number
1
2
3
4
5
6
7
8
9
Type ((
Distilled
Distilled
Distilled
Effluent
Effluent
Effluent
Effluent
Effluent
Effluent
fime
Jays)
30
30
30
56
30
30
56
30
56
Normal Stress
(kPa)
67.8
45.1
24.4
67.7
45.1
24.4
45.4
67.8
24.4
Shearing Force @ @ 125 mm*
125 mm Displacement Displacement
(Newtons) (degrees)
246.8
170.5
92.6
236.0
159.3
112.9
186.9
242.8
105.9
24.2
25.0
25.1
23.3
23.6
29.8
26.9
23.9
28.2
$ = friction angle
TABLE
Sample
Number
1
2
3
4
5
6
7
8
9
7. SHEAR TEST DATA
Treatment
Type
Distilled
Distilled
Distilled
Effluent
Effluent
Effluent
Effluent
Effluent
Effluent
Void
Ratio
0.549
0.540
0.535
0.561
0.541
0.544
0.557
0.542
0.551
FROM THE NIBLEY SAND SAMPLES
Normal Stress
(kPa)
24.4
24.4
24.5
24.6
24.4
24.4
24.4
24.4
24.4
Peak Point
Shearing Force
(Newtons)
417.8
400.5
418.0
333.1
467.9
420.8
384.3
427.5
441.95
TREATED FOR 28 DAYS
Relative Peak
Point *
(degrees)
64.7
63.7
64.6
59.1
67.1
64.9
62.8
65.2
65.9
= friction angle
30
-------
TABLE 8. SHEAR TEST DATA FROM THE SMITHFIELD CLAY SAMPLES
Sample
Number
1
2
3
4
5
6
7
8
9
Treatment Normal Load
Type (Newtons)
Distilled
Distilled
Distilled
Effluent-
Distilled
Effluent-
Distilled
Effluent-
Distilled
Average
Effluent
Effluent
Effluent
Average
194.9
195.1
195.2
194.9
195.3
195.1
194.7
195.1
195.2
Maximum Ratio of
Shearing Maximum Shearing Force
Force
(Newtons)
97.3
109.9
94.6
105.9
102.0
106.8
109.4
104.8
109.4
Normal Load
0.499
0.563
0.485
0.543
0.522
0.547
0.562
0.537
0.560
shown in Figure 17. Figures 18 through 20 show individual curves of shearing
force versus displacement for each of the Nibley sand samples. Figures 21
through 23 show the shearing force versus displacement curves for the
Smithfield clay samples.
Discussion of Shear Test Results
Water Quality Analysis for Shear Strength Samples
At the time new water was placed in the reservoir bottles, during the
treatment period, samples were taken of the distilled water, the old effluent,
and the fresh effluent just obtained from the sewage treatment plant. Water
quality tests were performed on both the effluent samples and the sample of
distilled water. In the analysis of the results of these tests, the data
from the fresh effluent samples and the old effluent sample were combined
to obtain an average value for each particular test. The test results are
presented in Tables 3 and 4. Water samples were analyzed only during the
first 24 days of the treatment period for the Tooele silt samples. Water
samples were analyzed throughout the entire treatment period for the Nibley
sand samples. Water samples were not analyzed for the Smithfield clay
samples.
During this study, the BOD5 ranged from 3.8 mg/£ to 29.7 mg/£ with an
31
-------
CO
ro
250-
50
0
549. IN
o Distilled water
A Effluent - 30 days
° Effluent - 56 days
O Sample number
366.2 N
197.6 N
Avg.
Normal
Load
10 15
DISPLACEMENT (mm)
20
25
Figure 16. Shearing force versus displacement curves for the Tooele silt.
-------
co
CO
5001 NIBLEY SAND
0
Normal load - 200 N
3456
DISPLACEMENT (mm)
8
Figure 17. Shearing force versus displacement envelope for the Nibley sand.
-------
500
OJ
-p=.
-*> 400-
o>
c
u
or
e
o
<
UJ
300-
200-
100-
NIBLEY SAND distilled water
Void ratio
0.549
0.540
0.535
3456
DISPLACEMENT (mm)
8
Figure 18. Shearing force versus displacement.
-------
500i
400-
CO
c
o
300-
LU
O
a:
p
200-
or
en
100^
NIBLEY SAND effluent
Void ratio
0.561
0.541
0.544
23456
DISPLACEMENT (mm)
8
Figure 19. Shearing force versus displacement.
-------
500i
CO
en
-|400^
s
o>
c
UJ
O
ac
s
e>
2
or
<
LU
300
200
NIBLEY SAND effluent
Void ratio
0.557
0.542
0.551
3456
DISPLACEMENT (mm)
8
Figure 20. Shearing force versus displacement.
-------
I20i
00
x-» 100"
"co i w
c
"5
O)
~ 80-
UJ
O
ct:
e
g 60-
E
UJ
x 40-
C/)
f
/
/c
//'/
//
y
1
1
A
H
/\
M
A \\
?\ \
\ \
V^
V \v
XK^
x
Normal load
o Sample I = 194.9 N
A Sample 2= 195.IN
a Sample 3= I95.2N
20-
0
468
DISPLACEMENT (mm)
10
12
Figure 21. Shearing force versus displacement curves, Smithfield clay distilled water treatment.
-------
CO
CXI
I20i
1001
*co
I 80-1
60-
LU
O
or
c
o
UJ
40-
20-
Normal load
Sample 4= 194.9 N
Sample 5= 19 5.3 N
Sample 6= 195. IN
468
DISPLACEMENT (mm)
10
12
Figure 22. Shearing force versus displacement curves, Smithfield clay, effluent - distilled water
treatment.
-------
CO
i-D
120-
100-
I 80-
60-
or
LU
40-
20
Normal load
o Sample 7= 194.7 N
A Sample 8= 195. IN
a Sample 9= 195.2N
468
DISPLACEMENT (mm)
10
12
Figure 23. Shearing force versus displacement, Smithfield clay effluent treatment.
-------
average value of 15.3 mg/H. The SS varied from 7.2 mg/£ to 18.3 mg/£ and
averaged 10.4 mg/£. These concentrations are well below the federal
standards for secondary treated effluents [U.S. Government, 1973]. The
high quality of the effluent may have had a restrictive effect on biological
growth in the samples.
Shearing Force Versus Displacement Curves--
Tooele silt --The shearing force versus displacement curves for the
Tooele silt samples, as shown in Figure 16, display a close comparison
between the results of those samples treated only with distilled water for
30 days and those samples treated only with effluent for the same period
of time. Because no major differences occurred between the two groups, the
remaining samples were not leached with distilled water but continued to
receive effluent for an additional 26 days before being sheared. Figures
13 and 15 show that after the initial 30 days, the flow through two of the
remaining three samples that had not been sheared (Sample Numbers 7 and 9)
had reduced to zero. This reduction of flow was attributed to the formation
of an insoluble gas as discussed by Lanae and Whisler [1972] and Rice [1974]
The gas was discovered by observing the formation and growth of air blocks
in the tubing connecting the water reservoir bottles to the bottom of the
shear cylinders. To resume the flow of effluent through these samples, the
hydraulic head on all three remaining samples was increased from 460 mm
(18 in.) to 910 mm (36 in.). Also, whenever such blocks occurred, the gas
was bled off in an attempt to resume the flow. This procedure was effective
in maintaining flow through the samples for the remaining 26 days of the
treatment period. Results of the tests on these last three samples after
56 days of treatment correspond with the results of the tests previously
performed after 30 days of treatment as shown in Figure 16.
The shearing force versus displacement curves for the samples of Tooele
silt show no more variation than would normally be found in tests on
samples having all received the same treatment.
Nibley sand--The normal pressure applied to all of the Nibley sand
samples was 24.4 kPa (3.53 psi), with only slight variations occurring
among the samples. The shearing force versus displacement curve for each
of the samples lies within the envelope shown in Figure 17. The maximum
shearing force indicated by this envelope is 467.9 N (105.15 Ibs) and the
minimum is 333 N (84.85 Ibs). The relationship between the void ratio and
the peak shearing force for the sand samples, is shown in Figure 24. The
maximum residual strength is 240.6 N (54.07 Ibs) and the minimum is 211.7 N
(47.58 Ibs). The shearing force versus displacement curves are all similar
in shape and exhibit typical results of a very dense sand. However, the
peak point friction angle, , is exceptionally high in each of the tests.
These values of varied from 59.1° to 67.1° (Table 7). It was later
determined that the point of application of the shearing force on the shear
box was too high. After making this modification to the apparatus, correct
values of could be measured. For the purpose of this study, however, the
relative results between the samples treated with distilled water and those
treated with effluent were of primary concern. The peak point shearing
angles obtained allowed a comparison of shear strength between different
40
-------
?
-------
treatment methods and did not influence the conclusions of this study.
For the purpose of maintaining uniformity among the sand samples, all
samples were prepared to a high density by placing them on a high frequency
vibrating table. The densities approached 100 percent relative density.
This preparation procedure was successful in obtaining uniform samples with
void ratios varying only between 0.535 and 0.561. However, by obtaining
such high densities, any effects of chemical or biological activity in the
porewater of the soil samples caused by the application of the treated
effluent may have been partially or totally masked.
Smithfield clay --The normal pressure applied to all of the Smithfield
clay samples was approximately 24 kPa (3.49 psi) with only slight variations
occurring among the samples. The maximum shearing resistance generally
occurred at a strain of approximately 1.25 percent. The samples were
sheared quickly and therefore the strengths measured represent the undrained
shear strength. Even though the normal loads only varied between 194.7 N
(43.76 Ibs) and 195.3 N (43.89 Ibs) (0.3 percent) the best comparison of
shear strength between the samples is the ratio of maximum shearing force to
normal force. These results are shown in Table 9. As indicated in Table 9,
the samples treated with sewage effluent showed a slightly higher shear
strength than the samples subjected to distilled water only. The average
ratio of shearing force to normal force varied from 0.516 for the distilled
water samples to 0.553 for the samples leached with sewage effluent. This
is about a 7 percent difference. The three samples that were leached with
sewage effluent followed by distilled water had an average ratio of shearing
force to normal force of 0.537.
TABLE 9. COMPARISON OF SHEAR TEST RESULTS FOR SMITHFIELD CLAY
Mean Ratio of c. , ,
Treatment Standard
Maximum Shearing Stress Deviation
Normal Stress
Distilled water only for 0.516 0.028
92 days
Effluent for 63 days followed 0.537 0.022
by distilled water for 27 days
Effluent only for 92 days 0.553 0.011
42
-------
CONSOLIDATION CHARACTERISTICS
General
Consolidation and permeability tests were performed on treated samples
of Tooele silt and Smithfield clay. The compressibility, rate of consolida-
tion, and permeability of the silt increased with application of the sewage
effluent whereas the clay samples were not appreciably affected by applica-
tion of the sewage effluent.
Quantity of Water Added to the Samples
The total accumulated volume of distilled water and/or treated sewage
effluent applied to each consolidation sample of Tooele silt is shown in
Figures 25 through 29. The total volume (7) of each sample and the computed
volume of the voids (vv) in each sample is also shown on these figures.
Samples 1C, 2C and 3C received effluent for 23 days and were then tested.
Samples 4C, 5C and 6C received effluent for 23 days, distilled water for an
additional 50 days, and were then tested. Samples 7C, 8C and 9C received
distilled water for 60 days and were then tested.
^ 1200-
o
o
800-
U_
U.
UJ
400-
I
Sample
2
i 0
o 0
V 442 cc 464cc
Vv I92cc 203cc
Sample
- I
2
° 3
425cc
I84cc
10 20 30
TIME (days)
40
Figure 25. Tooele silt, cumulative effluent versus time.
43
-------
2000i
-o I6oo^
o
1200-
LJ
> 800-
o
400^
10
Effluent
Distilled water
20 30
TIME (days)
Sample
4
V =427cc
Vv= I83cc
40
50
Figure 26. Tooele silt, sample 4C cumulative water versus time.
44
-------
2000i
o I600H
cc
LU
1200
LU
^ 800-
o
400-
10
Effluent
Distilled water
20 30
TIME (days)
40 50
Sample
5
V=399cc
Vv=l68cc
Figure 27. Tooele silt, sample 5C cumulative water versus time.
45
-------
2000i
1600-
1200-
LU
800
400
0
0
10
Effluent
Distilled water
20 30
TIME (days)
40
50
Sample
6
V =447cc
Vv = l86cc
Figure 28. Tooele silt, sample 6C cumulative water versus time.
46
-------
3000i
o
o
2500-
o:
Id
-------
The total accumulated volume of distilled water and/or treated sewage
effluent applied to each sample of Smithfield clay is shown on Figures 30
through 34. The total volume (v) and volume of the voids (vv) is also
shown on each figure. Samples 1C, 2C and 3C were leached with sewage
effluent for 38 days and then tested. Samples 4C, 5C, and 6C were leached
with sewage effluent for 34 days and then distilled water for an additional
20 days and then tested. Samples 7C, 8C and 9C were leached with distilled
water for 21 days and then tested.
o
300i
UJ
3 zocH
t
UJ
UJ
1
o
IOCH
0
Sample 2C
Sample IC,3C
0
10 20 30 40
TIME (days)
V
VtJ
J_
97cc
64cc
Sample
2.
90 cc
59cc
3.
85cc
55cc
Figure 30. Smithfield clay cumulative effluent versus time.
48
-------
300i
"o
o
200-
LU
p 100-
-------
300i
u
o
t!2oo^
i
LJ
P 100^
0
Distilled water
Effluent
10 20 30
TIME (days)
V =!03cc
Vv= 67 cc
40
Figure 33. Smith-field clay, sample 6 cumulative water versus time.
LJ LJ
I
200i
IOOH
8 o
Sample 8
Sample 7
Sample 9
0 10 20 30
TIME (days)
Sample
I 8. 9.
V Il2cc 98cc I07cc
Vv 72cc 63 cc 69cc
Figure 34. Smithfield clay, cumulative distilled water versus time.
50
-------
Quality of Water Added to Samples
Effluent was collected from the Preston Sewage Treatment Plant twice a
week in the morning by placing a container in the flow as it left the
chlorine contact chamber. The chemical composition of the effluent as well
as the distilled water is shown in Table 3. Only the chemical analysis for
the effluent used on the Tooele silt samples is shown. The results for the
Smithfield clay samples are not available; however, the Preston Municipal
Sewage Treatment Plant was the sole source of the wastewater effluent and
it is reasonable to assume that the effluent applied on the Tooele silt had
the same characteristics as that applied on the Smithfield clay.
Dimensions of Samples
The initial heights and the cross-sectional areas of all the samples
are shown in Tables 10 and 11. The initial height is the height of the
sample after consolidating under the initial 156.1 kPa (22.9 psi) load and
after being subjected to the appropriate treatment. As the tables show,
the nominal diameter of 101.6 mm (4 in.) varied slightly.
Consolidation Tests
The purpose of consolidation tests is to obtain soil data which can be
used to predict the amount and rate of settlement of soil deposits subjected
to an increase in intergranular pressure.
It is a well known characteristic of clays that a time lag occurs
between the application of a load and the compression of the clay layer. Two
factors contribute to this time lag, a hydrodynamic lag and a viscous lag.
Although these two phenomena occur simultaneously, the compression is usually
divided into primary and secondary phases. Primary consolidation is
TABLE 10. DIMENSIONS OF TOOELE SILT SAMPLES USED IN CONSOLIDATION AND
PERMEABILITY TESTS
Sample Initial Height Diameter Area
Number (mm) (mm) (mm)2
1 54.9 101.1 3028
2 57.4 101.3 8060
3 52.6 101.3 8060
4 53.1 101.3 8060
5 49.3 101.3 8060
6 55.6 101.3 8060
7 52.8 101.3 8060
8 57.2 101.3 8060
9 54.1 101.1 8028
51
-------
TABLE 11. DIMENSIONS OF SMITHFIELD CLAY SAMPLES USED IN CONSOLIDATION AND
PERMEABILITY TESTS.
Sample
Number
1
2
3
4
5
6
7
8
9
Initial Height
(mm)
11.9
11.2
10.4
11.7
11.9
12.4
14.5
11.9
13.2
Diameter
(mm)
101.1
101.3
101.1
101.3
101.3
101.3
101.3
101.3
101.3
Area
(mm)2
8028
8060
8028
8060
8060
8060
8060
8060
8060
attributed to hydrodynamic lag and secondary consolidation to viscous lag.
Figure 35 illustrates these two types of consolidation phases. The rate of
primary consolidation is generally described by the coefficient of consolida-
tion GV. Secondary compression has been related to the final slope of the
strain versus log of time curve, as [Buisman, 1936].
A prediction of the magnitude of compression can be obtained from the
void ratio versus the log of intergranular pressure curve (or the strain
versus the log of intergranular pressure curve). The slope of this curve
for normally consolidated soils is the compression index, C0,
The strain (e) versus log of effective pressure (a) relationships were
determined from the strains at the end of each load increment. These
graphs are shown in Appendix A. The strain was found by dividing the final
dial reading for that load increment by the original height of sample. The
average curves shown on Figures 36 and 37 were determined by averaging the
values of e at each load for each treatment type and plotting against the
log of the applied pressures. The slope of the e-log a curves is defined
as C and is related to the compression index, Cai by c = CC/C\ + e0), where
e0 is the initial void ratio [Dunn, et al. , 1979],
Tables 12 and 13 give the values of c for the different soils and treat-
ments. The . values for the clay samples were slightly curved and,
therefore, the higher pressure portions of the e versus log a graphs were
averaged to evaluate C for the clay.
The cv values were determined from the dial reading versus the log of
time curves for each loading increment. There are two curve-fitting
procedures commonly used to determine cv, the square-root-of-time fitting
method and the logarithm of time fitting method [Taylor, 1948]. The
logarithm of time method was employed for this study. For the purpose of
illustration, a typical graph is shown in Figure 35, and the graphical
52
-------
en
CO
4.Ch
e 4.5H
J
CD
O
LU
or
5.0-
d =5.161
5.5
fOI
1.0
\
_d0= 4.224
\
t50=36min
primary A
consolidation
secondary
consolidation v
10
TIME (minutes)
100
1000
Figure 35. Dial reading versus time. (Smithfield clay sample # 9C)
-------
0.0
10
20 40
100
200 400
o.i-
0.2-
0.3
0.4
- - distilled
effluent
leached
~ .08i
M
.10-
.1 I
distilled A
effluent
leached
10 20 40 100 200
EFFECTIVE PRESSURE (kPa)
Figure 36. Smithfield clay, average values of strain and QV versus
effective pressure.
400
54
-------
10 20 40 100 200 400
5 0.05H
^
a:
h-
co
0.10-
O-i
10-
20-
= 30-
distilled water
9^.^
effluent ' ^0_ V. \
o Yv-o
o
leachec
40-
effluent
10 20 40 100 200 400
EFFECTIVE PRESSURE (kPa)
Figure 37. Tooele silt, average values of strain and ov versus effective
pressure.
-------
TABLE 12. SLOPE (c) OF THE STRAIN VS LOG OF EFFECTIVE STRESS CURVE FOR
TOOELE SILT
Treatment
Sample
C
Cavg
Standard
Deviation
Distilled
789
0.092 0.085 0.085
0.0873
0.0040
Effluent
1 2 3
0.0943 0.0910 0.0955
0.0936
0.0023
Leached
456
0.1015 0.0980 0.094
0.0978
0.0038
TABLE 13. SLOPE (c) OF THE STRAIN VS LOG OF EFFECTIVE STRESS CURVE FOR
SMITHFIELD CLAY
Treatment
Sample
C
^avg
Standard
Deviation
Distilled
789
0.279 0.300 0.279
0.286
0.012
Effluent
1 2 3
0.275 0.289 0.283
0.282
0.010
Leached
4 5
0.283 0.274
0.279
0.005
6
0.279
technique for finding ov by the logarithm of time fitting method is shown.
The dial reading representing 100 percent primary consolidation is at the
intersection of the straight line portions of the middle and end of the
graph. Since the initial shape of the consolidation curve represents a
parabola, the dial reading at time zero is found by choosing two times ta
and tb on the early part of the curve in the ratio ta/tb = 0.25. The zero
time dial reading is located a distance above point a equal to the difference
in dial readings between the two. The point representing 50 percent primary
consolidation then lies halfway between 0 percent and 100 percent. The
coefficient of consolidation, cv, is calculated by the equation:
a =
v
£5 o
where tso is the time at 50 percent consolidation and HDP is the length of
the longest drainage path of the sample.
56
-------
The value of ov varies with each load increment. Appendix B shows o^
plotted against the average pressure of the load increment. Because of the
flat shape of the dial readings versus log time curves for the first load
increment of the clay samples, ov values were not determined for that
increment. Figures 36 and 37 show the average values of ov for each soil
and type of treatment. Tables 14 and 15 give the cv values for the average
of each pressure increment and the standard deviations from the average.
The mechanism of secondary consolidation is not well defined. However,
it is probably associated with an interaction of the double layers associated
with an interaction of the double layers associated with each clay particle.
Dunn and Anderson [1976] explain this secondary consolidation as a viscous
resistance to deformation and suggest that it is composed of a volumetric
resistance component and a shear resistance component.
The secondary rate of consolidation for this study (a ) is defined as
S
£2 - £1
a, =
s log ti - log t\
and is the slope of the straight line end portion of the dial reading - log
time curve divided by the original height of sample. There is a value of
as associated with each load increment and these values are given in Tables
16 and 17. The average as values for each of the three treatments and soil
types are shown in Figures 38 and 39.
Permeability
Permeability is a soil characteristic that is closely associated with
the consolidation characteristics of the soil. The higher the permeability,
the greater the rate of consolidation. Permeability is expressed by the
coefficient of permeability k and is a property of the soil which indicates
the ease with which water will flow through the soil. The permeability test
results are shown in Tables 18 and 19.
Soil Chemistry Considerations
The proportion of sodium in the adsorbed layer has an important bearing
on the structural status of a soil [Olson and Mesri, 1970; Mitchell, 1976;
Lambe, 1958; Mesri and Olson, 1971]. It is often described in terms of the
exchangeable sodium percentage (ESP), defined as
ESP = Total Exchange Capacity (CEC) x 100%
Another means of expressing the concentration of Na ions on the adsorbed
surface is through the sodium adsorption ratio (SAR) of the soil solution,
which is defined as Ma+
SAR - -/-
Ca++
2
57
-------
TABLE 14. VALUES OF THE COEFFICIENT OF CONSOLIDATION (a ) FOR SMITHFIELD
CLAY IN (mm2/min) v
Treatment c ,
_ Sample
Type p
7
8
Distilled 9
Water
Avg.
Stan. Dev.
1
Effluent ^
Avg.
Stan. Dev.
4
5
Leached 6
Avg.
Stan. Dev.
Average Normal Stress (kPa)
29.7 58.9 117.4 233.5
9.03
7.94
8.45
8.45
0.548
8.19
9.10
8.71
8.65
0.453
8.90
8.45
9.29
8.90
0.420
9.48
8.77
8.77
9.03
0.410
8.58
9.10
9.42
9.03
0.423
9.68
8.77
8.90
9.10
0.488
10.26
9.16
9.74
9.74
0.548
9.16
9.48
9.61
9.42
0.233
10.58
9.74
10.07
10.13
0.423
10.07
10.13
10.13
10.13
0.0372
9.16
10.52
9.81
9.81
0.677
11.23
9.29
10.97
10.52
1.05
TABLE 15. VALUES OF THE COEFFICIENT OF CONSOLIDATION (GV) FOR TOOELE SILT
IN (irim2/min)
Treatment
Type
Distilled
Water
Effluent
Leached
Sample
7
8
9
Avg.
Stan. Dev.
1
2
3
Avg.
Stan. Dev.
4
5
6
Avg.
Stan. Dev.
16.3
3.03
-_
3.42
3.23
0.271
2.84
4.13
2.39
3.10
0.903
1.74
1.94
3.81
2.52
1.136
Average
29.5
10.00
9.29
9.42
9.55
0.381
10.84
14.13
11.74
12.26
1.697
6.91
8.13
8.58
7.87
0.865
Normal
58.7
15.36
12.39
12.52
13.42
1.678
14.77
18.45
16.97
16.71
1.845
11.16
14.52
16.26
14.00
2.587
Stress (kPa)
117.4
19.94
17.27
19.16
18.78
1.394
21.55
23.94
23.87
23.10
1.355
15.10
15.27
25.10
18.45
5.736
233.8
33.03
25.16
24.45
27.55
4.762
32.65
54.52
37.10
41.42
11.55
20.58
22.90
32.19
25.28
6.181
58
-------
TABLE 16. VALUES OF a FOR SMITHFIELD CLAY IN (10"3)
Treatment Sample
7
B
Distilled 9
Water
Avg.
Stan. Dev.
1
Effluent 2
Avg.
Stan. Dev.
4
5
Leached 6
Avg.
Stan. Dev.
39.5
13.2
14.7
16.8
14.9
1.81
15.1
14.7
12.7
14.2
1.29
13.0
13.8
15.4
14.1
1.22
Total Normal
78.6
9.0
9.2
9.2
9.1
0.12
10.5
10.4
7.2
9.4
1.88
8.0
7.7
7.4
7.7
0.30
Stress
156.2
6.4
7.1
7.3
6.9
0.47
6.3
6.6
5.8
6.2
0.40
6.5
6.6
6.4
6.5
0.10
(kPa)
311.4
3.7
4.2
4.4
4.1
0.36
3.6
4.1
2.6
3.43
0.76
7.0
2.6
3.8
4.5
2.27
Ch
b
locH
150^
o effluent
° leached
A distilled
10 20 40 100 200
EFFECTIVE PRESSURE (kPa)
Figure 38. as versus effective pressure for Smithfield clay samples
59
400
-------
TABLE 17. VALUES OF a, FOR TOOELE SILT IN (10~3)
o
Treatment
Type
Distilled
Water
Effluent
Leached
Sample
7
8
9
Avg.
Stan. Dev.
1
2
3
Avg.
Stan. Dev.
4
5
6
Avg.
Stan. Dev.
19.6
3.02
2.05
2.73
2.60
0.497
3.56
3.53
3.72
3.55
0.102
4.01
3.20
2.88
3.36
0.582
Total
29.3
2.88
2.67
3.01
2.85
0.171
2.08
1.94
2.17
2.06
0.120
2.72
2.73
2.06
2.50
0.383
Normal Stress (kPa)
78.1 155.8 311.8
2.64
2.22
2.82
2.56
0.307
2.54
2.56
2.66
2.59
0.064
3.01
2.47
2.93
2.80
0.291
1.92
1.78
2.26
1.99
0.246
2.45
1.77
2.80
2.34
0.523
2.48
2.73
2.70
2.64
0.137
2.98
2.36
2.59
2.64
0.313
2.54
2.65
2.75
2.65
0.105
2.48
3.09
2.51
2.69
0.343
200-
250
x 30^
G
350-
400
distilled
leached
sewage
10 20 40 100 200
EFFECTIVE PRESSURE (kPa)
Figure 39. as versus effective pressure for Tooele silt samples.
60
400
-------
TABLE 18. PERMEABILITY (k) FOR TOOELE SILT
Sample
Number
1
2
3
4
5
6
7
8
9
Leachant
Effluent
Effluent
Effluent
Effluent/Distilled Water
Effluent/Distilled Water
Effluent/Distilled Water
Distilled Water
Distilled Water
Distilled Water
k
( cm/mi n x 10~6)
6.58
7.22
6.42
4.55
5.43
7.75
7.69
3.92
5.60
Average k
(cm/min x io~6)
6.74
5.91
5.74
TABLE 19. PERMEABILITY (k) FOR SMITHFIELD CLAY
Sample
Number
4
5
6
7
8
9
Leachant
Effluent/Distilled Water
Effluent/Distilled Water
Effluent/Distilled Water
Distilled Water
Distilled Water
Distilled Water
k
( cm/mi n x 10~7)
1.89
1.88
1.96
2.17
1.99
2.89
Average
( cm/mi n x 1
1.91
2.35
k
o-7)
For the results of the chemical analysis of the soil, it was possible to
calculate the ESP and SAR values for all the samples. These results are
shown in Table 20. The amount of extractable calcium shown includes calcium
from carbonates since lime was present in the samples and the ammonium
acetate extraction procedure employed brings some of that lime into solution
resulting in increased extractable Ca++ values. For this reason, the SAR
values were calculated from only the water soluble ions and, therefore, are
not as good an indication of the soil's actual chemical state as are the
ESP values.
When the exchangeable sodium percentage, ESP, of a soil is increased
to about 15 percent or greater, a breakdown in the physical structure of
the soil may occur. In the presence of a high salt concentration in the
soil, the sodic hazard is minimized and the infiltration and permeability of
the soil usually remains near its highest values in spite of the increase in
ESP- The problem arises when the salt is removed, e.g., by reclamation, and
the high exchangeable sodium causes a breakdown of the physical condition of
61
-------
TABLE 20. RESULTS OF SOIL CHEMISTRY TESTS
en
ro
Treatment
Effluent
Effluent
Leached
Leached
Distilled
Water
Distilled
Water
Effluent
Effluent
Leached
Leached
Distilled
Water
Distilled
Water
None
Tooele Silt
Sample #
#1
#3
#5
#6
#7
#9
Smith field
Clay Sample 1
K
#3
#5
#6
#8
#9
110
Soluble
H20-Soluble meq/100 g
Ca Mg Ma K
.1 .1 10
.1 .1 .1 0
.1000
.1000
.1000
.1000
5.9 1.3 5.8 .5
3.5 .9 5.3 .3
5.5 1.6 7.4 .6
3.5 .9 5.3 .3
5.4 1.2 9.2 .7
1.9 .4 4.8 .2
.4 .3 6.7 .2
SAR
.32
.32
0
0
0
0
3.06
3.57
3.93
3.57
5.06
4.48
11.33
Extractable
NH,)OAC meq/100 g
Ca Mg Na K
34 3.7 .6 .6
41 3.7 .5 .6
37 3.6 .4 .6
39 3.4 .3 .5
36 2.9 .3 .5
38 3.4 .3 .6
46.8 6.5 11.7 1.4
40.7 6.1 11.4 1.4
49.0 6.6 13.2 1.5
29.6 5.9 9.7 1.4
47.2 6.4 12.8 1.5
34.3 5.8 11.6 1.5
44.1 6.5 19.2 1.6
ESP
3
3
3
2
2
2
24.6
28.1
25.3
21.0
15.5
28.8
54.8
CEC
15.3
12.9
13.6
15.7
14.0
17.3
24.0
21.7
22.9
21.0
23.3
23.6
22.8
-------
the soil. This breakdown in the soil structure is the result of the swelling
of clays and eventual dispersion of the soil fraction. The effect of the
swelling and dispersion is to effectively plug the conducting pore system of
the soil ma.trix by lodged particles, thereby reducing the hydraulic conducti-
vity to a very low level. The mechanism by which the sodium ion promotes
swelling-dispersion is based on the repulsion of the clay particles when
their sodium-ion-dominated diffuse double layers interact. The presence
of salts with higher valence tends to compress the double Jayer, to make it
more dense, thereby reducing the repulsion between clay particles [Jurinak,
1976]. The physical condition of all soils is not affected equally as the
ESP increases. Montmorillonite, however, which is a highly expansive clay,
is highly sensitive to the ESP change. Shear strength, permeability and
consolidation may all be adversely affected by the high ESP of a montmorillo-
nite clay.
Discussion of Consolidation and
Permeability Test Results
General --
The problem was to decide whether or not the average values of the
consolidation parameters were statistically different between the three
types of treatment. Towards this end an analysis of variance study was
done on the C and o values for each type of soil. A computer program from
the computer science5 department at Utah State University was utilized. It
may be treated as a problem of testing the Null hypothesis that all the
mean values for each parameter were equal. Testing for a difference in the
C values was relatively simple. If a difference was found in the type of
treatment, a least significant difference analysis was performed to
determine where the difference occurred. However, the cy values varied not
only with the type of treatment but also with the effective stress. To
adequately analyze the av values, three differences in ov were allowed for:
Difference between treatments
Difference between effective stresses
Difference between treatments with a common effective stress.
As with the C values, once a difference in ov was determined to be signifi-
cant, a least difference analysis was performed to determine where the
difference occurred.
Tooele silt --
For the Null hypothesis to be rejected and the differences to be
significantly different at the a level, the calculated F value must exceed
the tabular a value. The analysis of variance results, at the 0.10 level,
show that there is a significant difference between the average values of C
corresponding to the three treatments. Furthermore, the least significant
difference test (a - 0.10) indicates that this difference was between
treatment 1 (distilled water) and treatment 2 (effluent) as well as between
treatment 1 and treatment 3 (leached). Thus, it can be said with a 90
percent degree of confidence that the application of effluent increased the
63
-------
compressibility of the silt. However, since there was no significant
difference between the leached values of c and the effluent treated c values,
this increase in compressibility was not reversible.
In like manner, the analysis of variance test, at the 0.10 significance
level for the ov values indicates there was a significant difference between
treatments as well as a significant difference between treatments with a
common stress. The least significant difference test (a = 0.10) shows that
there was a significant difference between treatment 2 (effluent) o^ values
and the other two treatment values of ov. An additional least significant
difference test (a = 0.10) indicates that this difference is significant
only at the 2806 kPa (407 psi) effective stress level. Therefore, it can
be said with a 90 percent degree of confidence that at the average effective
stress of 2806 kPa (407 psi) there was an increase in the av value. Further-
more, since the average av values for the effluent were significantly
different from the average values of the leached samples, it can also be
said with a 90 percent degree of confidence that this increase in ov from
application of the effluent was reversible.
As would be expected, the results also show that the average values of
ov were significantly different between different average effective stresses.
This increase in rate and compressibility of the silt with application
of the effluent can probably be attributed to biological conditions rather
than chemical changes in the soil. Table 20 shows that the ESP values for
the silt were very low. One possible explanation for the increased
compressibility would be the formation of slimes on the silt particle
surfaces which would reduce the inter-particle friction and thus help make
the particles slip past each other. However, the high quality of the
effluent may make this an unreasonable hypothesis.
Figure 39 shows that the rate of secondary consolidation for the Tooele
silt appears to be independent of both consolidation pressures as well as
the type of treatment.
The Tooele silt showed an increase in permeability with application of
sewage in Table 18. This does not agree with the results of past researchers
but is, however, consistent with the consolidation test results of this
study. Since the ESP values for the silt were all so low, this increase in
permeability was probably not due to a decrease in the double layer thickness.
Smithfield clay --
The analysis of variance test applied to the Smithfield clay shows that
there was no significant difference between any of the mean C values or mean
cv values. The consolidation properties of the Smithfield clay samples were
not affected by the effluent. The only significant difference shown was the
difference in ov as the effective stress increased.
Table 20 shows that the clay samples, sample IOC in particular, have
high ESP values. Sample IOC was a control sample. It was a dry Smithfield
clay that had not been subjected to any treatment. Its high ESP of 54.8
64
-------
percent indicates that the Smithfield clay samples were in a potentially
highly dispersable state prior to treatment and upon remolding (i.e., mixing
with distilled water) became highly dispersed. The ESP values for samples
8C and 9C which were leached with distilled water'are both well below that
of sample IOC. It would seem logical to assume that the ESP values for
samples 8C and 9C would have been the same as the ESP for sample IOC and
for all the samples prior to treatment. Furthermore, since all the ESP
values were approximately the same and all lower than sample IOC, this would
indicate that the application of either effluent or distilled water lowers
the ESP of the soil from its original high value resulting in a more
permeable and less compressible soil. The uniformity of the ESP values was
consistent with the uniformity of the c and ov values.
The secondary consolidation rate for the Smithfield clay showed a
definite decrease as the consolidation pressure increased as evidenced by
Figure 38. The type of treatment, however, did not appear to have any
effect. This observed decrease in rate with an increase in pressure was
consistent with findings by Shiffman, et al. [1964]^on an investigation of
a Vicksburg Buckshot clay.
As has been pointed out, the Smithfield clay was initially a potentially
highly dispersable clay shown by the ESP value .of sample IOC. Upon applica-
tion of either type treatment, the ESP values for all the samples were
reduced and thus made more permeable due to the exchange of sodium ions
which resulted in a thinner double layer which creates more free pore water.
The permeability coefficient k for both the leached and distilled water
treated samples were fairly close as would be expected since the ESP values
for the two treatments were the same.
It is possible that the ESP values reported for the different treat-
ments had not reached equilibrium and some or all values might have decreased
even more from the original values had they been leached for a longer period
of time. This may have resulted in arriving at different equilibrium
points for the different treatments.
Permeability tests were not performed on the effluent treated clay
samples since it was feared that the distilled water used for the permeability
test would alter the chemical state of the treated soil.
Example Problem
The following example problem is included as a means of illustrating how
the differences in the consolidation characteristics of the Tooele silt
would affect the settlement of an idealized soil profile of Tooele silt
such as that shown in Figure 40.
Figure 41 shows the amount of expected settlement plotted against time
for the Tooele silt saturated with distilled water and with the wastewater
effluent. The computations were based on values of c and Cy obtained from
Tables 12 and 15. The ultimate settlement for a soil profile that had been
leached with treated sewage would be approximately 68.6 cm (27 in.) with
65
-------
W/Tsz
12205 kg/m2 added load
Tooele Silt
12m
A>\\\\\\\\
\\ \ \\
\r
Figure 40. Hypothetical soil profile for example consolidation problem.
90 percent consolidation occurring in 2560 days. The ultimate settlement
for a soil profile that had been leached with distilled water would be
approximately 50.8 cm (20 in.) with 90 percent consolidation occurring in
3667 days.
66
-------
01
Oi
LJ
S
LJ
25-
50-
co
75
0
distilled water
1000
2000
TIME (days)
3000
Figure 41. Settlement versus time -- example problem.
-------
REFERENCES
Allison, L. E. 1947. Effect of microorganisms on permeability of soil
under prolonged submergence. Soil Science, 63:439-450.
Andersland, Orlando B., and P. John Matthew. 1973. Consolidation of high
ash papermill sludges. Journal of the Soil Mechanics and Foundations
Division, ASCE, Proc. Paper 9713. 99(SM5):365-374.
APHA, AWWA, WPCF. 1975. Standard Methods for the Examination of Water and
Wastewater. 14th Ed. Washington, D.C. 1193 p.
Aziz, M. M., A. Alvin Bishop, and I. S. Dunn. 1966. Influence of exchange-
able ions on the stability of drain banks. Transactions of the American
Society of Agricultural Engineers. 9(6):788-792.
Buisman, A. S. K. 1936. Results of long duration settlement tests.
Proceedings of 1st International Conference on Soil Mechanics and
Foundation Engineering. 1:103-106.
Day, A. D., J. L. Stroehlein and T. C. Tucker. 1972. Effects of treatment
plant effluent on soil properties. Journal of Water Pollution Control
Federation. 44(3):372-375.
de Vries, J. 1972. Soil filtration of wastewater effluent and the
mechanism of pore clogging. Journal of Water Pollution Control Federa-
tion. 44(4):565-573.
Dunn, I. S., and L. R. Anderson. 1976. Viscous resistance during consolida-
tion. Unpublished Report on a University Research Project, Department
of Civil and Environmental Engineering, Utah State University.
Dunn, I. S., L. R. Anderson, and F. W. Kiefer. 1979. Fundamentals of
Geotechnical Analysis. In press. John Wiley and Sons.
Jurinak, J. J. 1976. Soil science, 619 lecture notes. Utah State University
Lambe, T. William. 1958. The structure of compacted clay. Journal of the
Soil Mechanics and Foundations Division., ASCE, Proc. Paper 1654. 84
(SM2):l-34.
Lance, J. C., and F. D. Whisler. 1972. Nitrogen balance in soil columns
and intermittently flooded with secondary sewage effluent. Journal of
Environmental Quality. 1(2):180-186.
68
-------
Mesri, G., and R. E. Olson. 1971. Consolidation characteristics of
montmorillonite. Geotechnique, 21 (4) :341-352.
Mitchell, James K. 1976. Fundamentals of soil behavior. John Wiley and
Sons, Inc., New York. 422 p.
Olson, R. E., and G. Mesri. 1970. Mechanisms controlling the compressibility
of clay. Journal of the Soil Mechanics and Foundation Division, ASCE,
Proc. Paper 7649. 96(SM6):1863-1878.
Rice, Robert C. 1974. Soil clogging during infiltration of secondary
effluent. Journal of Water Pollution Control Federation. 46(4):708-716.
Schiffman, R. L., C. C. Ladd, and A. T-F. Chen. 1964. The secondary
consolidation of clay. International Union of Theoretical and Applied
Mechanics, Symposium of Rheology and Soil Mechanics.
Shainberg, I., and A. Caiserman. 1971. Studies on Na/Ca montmorillonite
systems 2. The hydraulic conductivity. Soil Science. 3(5):276-281.
Taylor, D. W. 1948. Fundamentals of soil mechanics. John Wiley and Sonc,
Inc., New York. 700 p.
U. S. Government. 1973. Federal secondary treatment standards. Federal
Register. 38(159):22298. U. S. Government Printing Office, Washington,
D.C.
69
-------
(S)
O.Oi
0. 1-
0.2-
0.3
0.4
0.5
APPENDIX A
STRAIN VERSUS EFFECTIVE PRESSURE
Smithfie d C ay
Sample 1
Sample 2
Sample 3
o 100 1000
EFFECTIVE PRESSURE (kPa)
Figure A-l. Smithfield clay, strain versus effective pressure, effluent.
-------
CO
0.0
Smithfie d C ay
o. 1-
0.2-
0.3-
0.4-
0.5-
Sample 4
Sample 5
Sample 6
10 100 1000
EFFECTIVE PRESSURE (kPa)
Figure A-2. Smithfield clay, strain versus effective pressure, leached.
71
-------
en
Smithfie d Clay
O.Ch
o.
0.2
0.3
0.4
0.5
Sample 7
Sample 8
Sample 9
Figure A-3.
10 100 1000
EFFECTIVE PRESSURE (kPa)
Smithfield clay, strain versus effective pressure, distilled
water.
72
-------
O.OOi
0.02-
0.04-
0.06i
0.081
0.
0.
0.14
T o o e e Si i
Sample 1
Sample 2
Sample 3
i 1ir
10 100 1000
EFFECTIVE PRESSURE (kPa)
Figure A-4. Tooele silt, strain versus effective pressure, effluent.
73
-------
T
o o e e
Silt
O.OOi
0.02-
0.04-
0.06-
or
0.08-
0.10-
0.12-
0.14
Sample 4
Sample 5
Sample 6
10 100 1000
EFFECTIVE PRESSURE (kPa)
Figure A-5. Tooele silt, strain versus effective pressure, leached.
74
-------
T
o o e I e
Si i
O.OOi
0.02-
0.04-
0.06-
cc
0.08-
0.10-
0.12-
0.14
Sample 7
Sample 8
Sample 9
10 100 1000
EFFECTIVE PRESSURE (kPa)
Figure A-6. Tooele silt, strain versus effective pressure, distilled water.
75
-------
O.OS-i
0.09-
0.10-
0. 1 1
0.12
O-08-i
0.09-
c, 0.10
E
~ 0.11
o> 0.12
0.08-]
0.09-
0.10-
0. 1 1-
0.12-
APPENDIX B
cv VERSUS EFFECTIVE PRESSURE FOR THE
SMITHFIELD CLAY AND TOOELE SILT SAMPLES
Smithfield Clay
Sample 1
Sample 2
Sample 3
Sample 4
Sample 5
Sample 6
Sample 7
Sample 8
Samp I e 9
10 100 1000
EFFECTIVE PRESSURE (kPa)
Figure B-l. Smithfield clay, o versus effective pressure.
v 76
-------
E
E
O
0
10-
20-
30-
40-
50
i
60
5
10-
15-
20-
25-
30-
35
5
10
15-
20-
25-
30-
35
Sample 1
Sample 2
Samp I e 3
Sample 4
Sample 5
Sample 6
Sample 7
Sample 8
Samp Ie 9
10 100
EFFECTIVE PRESSURE (UPa)
Figure B-2. Tooele silt, o versus log of effective pressure.
1 000
77
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TECHNICAL REPORT DATA
(Please read Instructions on the reverse before completing}
. REPORT NO.
EPA-600/2-79-171b
3. RECIPIENT'S ACCESSION-NO.
4. TITLE AND SUBTITLE
LONG-TERM EFFECTS OF LAND APPLICATION OF DOMESTIC
WASTEWATER: Tooele, Utah, Slow Rate Site
Vol. II: Engineering Soil Properties
5. REPORT DATF
August 1979 issuing date
6. PERFORMING ORGANIZATION CODE
7. AUTHOR(S)
Anderson, Loren R.
W. F. Campbell, D.
J. H. Reynolds, R. W. Miller,
G. Beck, and J. A. Caliendo
8. PERFORMING ORGANIZATION REPORT NO
9. PERFORMING ORGANIZATION NAME AND ADDRESS
Utah Water Research Laboratory
Utah State University
Logan, Utah 84322
10. PROGRAM ELEMENT NO.
1BC822
11. CONTRACT/GRANT NO.
68-03-2360
12. SPONSORING AGENCY NAME AND ADDRESS
Robert S. Kerr Environmental Research Lab - Ada, OK
Office of Research and Development
U. S. Environmental Protection Agency
Ada, Oklahoma 74820
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
EPA/600/15
15. SUPPLEMENTARY NOTES
is.ABST^A|c:j-gh quaiity secondary sewage effluent was applied to three soil types and its
effects on the shear strength, consolidation properties, and permeability of the soils
was studied. The three soil types were a poorly graded sand, a clayey silt, and a
highly plastic clay. Each soil was divided into nine samples. Six samples were leach-
ed with secondary sewage effluent and three with distilled water. Three of the
effluent samples were then re-leached with distilled water in order to investigate the
possibility of any reversible phenomenon.
After a suitable amount of leachate has passed through the samples, direct shear
tests, standard consolidation tests, and falling head permeability tests were per-
formed. The shear strengths of the sand and silt were not appreciably affected by the
application of wastewater. The shear strength of the clay was slightly increased by
the wastewater effluent. The compressibility, rate of consolidation, and permeability
of the silt increased with application of the effluent whereas the clay samples were
not affected by the application. Except for the rate of consolidation at high stress
levels, application of distilled water to treated samples did not reverse changes in
the above properties.
KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
c. COSATI Field/Group
Soil properties
Land use
Sewage treatment
Tooele, Utah"
Soil types
Land application
Sewage effluent
Soil mechanisms
Soil engineering
"SUIT
48E
68D
91A
91G
3. DISTRIBUTION STATEMENT
RELEASE TO PUBLIC
19. SECURITY CLASS (This Report)
UNCLASSIFIED
21. NO. OF PAGES
90
20. SECURITY CLASS (This page)
UNCLASSIFIED
22. PRICE
EPA Form 2220-1 (9-73)
78
US GOVERNMENT PRINTING OFFICE 1979 -657-060/5370
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