United States
Environmental Protection
Agency
Hazardous Waste Engineering _^- ^
Research Laboratory - ' ,A' -
Cincinnati OH 45268 r -\ \
Research and Development
EPA/600/S2-86/109 Mar. 1987
Project Summary
Geotechnical Analysis for Review
of Dike Stability (CARDS)
R. M. McCandless, A. Bodocsi, and P. R. Cluxton
The structure and capabilities of a
user-friendly, interactive computer pro-
gram developed for the stability analysis
of dikes (CARDS) are described. The
CARDS program is designed to guide a
geotechnical nonspecialist (EPA regula-
tory personnel) through customary
steps of earth dike analysis considering
slope stability, settlement, liquefaction,
hydraulic flow and pressure conditions,
and piping. The CARDS package is
designed for use on the IBM-PC/XT
"tar or compatibles.
Research Laboratory, Cincinnati, OH, to
announce key findings of the research
protect that Is fully documented In a
separate report of the same title (see
Protect Report ordering Information at
back).
suiting therefrom; ana
determine the critical exit gradient and
the potential for piping failure.
User documentation consists of a
combined Handbook/User's Manual
which presents basic theory program
operational procedures, and example
long hand and computer solutions for
each analysis.
This Project Summary was developed
by EPA's Hazardous Waste Engineering
Introduction
Geotechnical Analysis and Review of
Dike Stability (GARDS) is a user-friendly,
interactive computer software package
for the geotechnical analysis of dikes at
hazardous waste sites. GARDS was
""""-—-^veloped to meet an expressed need for
geotechnical software tool to evaluate
justing and planned earth dike structures
jt hazardous waste facilities. Moreover,
>e tool was designed for use by regula-
pry personnel with technical, but not
lecessarily geotechnical, background.
The GARDS package is suitable for use
as a design review tool where data
describing site conditions and soil pa-
rameters have been supplied by a geo-
technical professional.
Program Features
As developed, the GARDS software
package consists of several distinct blocks.
Each block is a program in itself and is
called by the user through the use of
menu displays. The main command struc-
ture of the GARDS program is as follows:
1. Control Block
2. Input Block
3. Input Data Check and Edit Block
4. Slope Stability Analysis Block
5. Settlement Analysis Block
6. Liquefaction Analysis Block
7. Summary Output Block
The following paragraphs present a brief
description of each of the major program
blocks.
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Control Block
The control block is the first block en-
countered by the user. It gives an in-
troduction to the program and other
program blocks. Its primary function is to
call the appropriate analysis block selected
by the user from a "command menu"
displayed on the screen. The menu is a
list of the input/output and analytical
options available to the user.
The Input Block
The input block is the first block to be
selected by the user and offers three
user-friendly options:
1. Initial data entry with text explana-
tions and graphical examples.
2. Initial data entry without text
explanations.
3. Data entry using an existing input
data file.
The first input option is designed to
guide the occasional user through the
initial data entry procedures. Explanations
and graphical examples of the types of
required input data are displayed on the
screen prior to data entry. The option to
review any or all explanations prior to
data entry is available to enable the user
to proceed at his or her own pace.
The second input option contains all of
the features of option one, except that
the text explanations and graphical
examples are not included. This option
would be selected for initial data entry by
the user who is experienced in the use of
GARDS and is therefore familiar with the
definitions of the required input data.
The third option is selected by the user
who previously entered all data using
options 1 or 2, has saved it on a data file,
and elects to use the analysis features of
the program at a later time. A listing of
the data files available to the user is
displayed. The data is assigned to the
appropriate program variables internally.
The use of this option eliminates the
repeated entry of basic soil property and
geometric data if the user wishes to re-
analyze a particular dike section under
different conditions.
An internal data check is performed
automatically with all input options to
verify that values of all input variables fall
within specified ranges. If the value of
the data item is not within the specified
range, an error message will prompt the
user to enter a value within the specified
range. Once notified, the user has the
option to override this error trap routine if
warranted.
Input Data Check and Edit Block
After one of the options of the input
block is used, the input data check and
edit block provides for general verification
and modification of input data. The user
may check or edit all or selected portions
of the input data in any existing data file.
Since, however, input and internally
generated data routinely are displayed as
part of the Summary Output Block (de-
scribed later), the primary function of this
block is to edit portions of existing data
files in order to model different conditions
for subsequent runs. This block is also
routinely used to conduct a visual check
of geometric continuity of the section
before proceeding with an analysis.
Hydraulic Block
The hydraulic block automatically deter-
mines the coordinates of the piezometric
surface for any of six idealized hydraulic
boundary conditions. The computations
for the hydraulic block are made at the
end of the input block so that the
piezometric surface data is available for
subsequent analyses. This block utilizes
an existing finite element based program
for solving steady-state problems of free
surface or confined flow of water in a
two-dimensional porous region. A sup-
port program was developed to internally
generate an input data file from the
general user-input data file. Another
support program was developed to utilize
the output exit gradient and to relay the
amount of seepage through the dike sec-
tion to the summary output block. The
potential for an uplift pressure failure of
an impermeable barrier such as a clay
liner is also determined and noted in the
summary output listing.
Slope Stability Analysis Block
The slope stability block used data
defining the piezometric surface from the
Hydraulic Block to perform either of two
conventional slope stability analyses. The
first is a rotational (circular slip surface)
analysis which used the Simplified Bishop
Methods of slices. The second is a trans-
lations! (plane slip surface) analysis.
The major features of the rotational
analysis include:
• Dike slopes of any configuration and
made up of up to 19 soil layers may
be analyzed.
• Seepage conditions modeled in the
form of the steady-state piezometric
surface through the section are
determined in the Hydraulic Block.
• Seismic effects may be included.
• The program has a radius centre
feature which produces trial circle
that fall between specified limit
defined by the soil layer geometry.
• The program conducts an automata
search for the minimum factor o
safety with trial arc centers specif iei
by internally-generated or user
defined grids, or by user-specifie<
centers.
The major features of the translationa
analysis option are the same as those fo
the rotational case except that the tria
surface consists of straight line segment!
which form the base of an active (thrust
ing) wedge, a neutral or thrusting centra
block, and a passive (restraining) wedge
The automatic search routine for this
analysis is based upon selection of a tria
central block defined by the surface aru
subsurface soil layer geometry, followec
by computation of the coordinates for the
associated active and passive wedges
The analysis proceeds over all soil layer:
in the section using a standard (auto-
matic) or user-defined increment to define
the location of subsequent trial centra
blocks.
Both stability analyses may be per-
formed using any of the six hydraulic
boundary conditions described earlier anc
may employ unconsolidated drained soi
strength parameters.
The results of the rotational analysis
are presented as a tabulation of all factors
of safety less than 2.5 along with the
corresponding coordinates of the various
failure arc centers, radii, and associatec
hydraulic boundary conditions. A plotting
subroutine plots the dike section, the
most critical circle passing through it, the
factor of safety, and other pertinent pro-
ject information.
Settlement Analysis Block
The settlement analysis block is used
to determine the compression of founda-
tion soils due to stresses caused by the
weight of an overlying dike. The settle-
ments are calculation using Boussinesq's
Theory and Terzaghi's One-Dimensional
Consolidation Settlement Theorem. Re-
quired soil parameters for each soil
include unit weight, initial void ratio,
compression and recompression indices,
and the over consolidation ratio.
Settlements are calculated at the toes,
crest points, and centerline of the dike.
The consolidation of each soil is calculated
for each layer and summed up for all
soils to determine the total settlement at
each point. Differential settlements are.
calculated between each toe and cresm
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toe and centerline, and crest and
centerline.
Liquefaction Block
The liquefaction block determines the
potential for liquefaction of the dike and
foundation soils. The procedure applies
mainly to site conditions involving sand
or silty sand strata occurring below a
level ground surface. The analysis uses
soil parameters routinely obtained during
site exploration and subsequent labora-
tory testing. Site seismic parameters may
be estimated using published guidelines
or may be obtained from site-specific in-
vestigation (preferred). The analysis uses
an automatic search routine controlled
by the section geometry to locate the
area of highest liquefaction potential.
Results are reported as a tabulation of
soil layers and points having a factor of
safety which is less than 2.50.
Summary Output Block
The summary output block allows the
user to obtain a hard copy of the input
data and the results of all analyses run
for the dike section under study. The
critical factors of safety, failure circle
center coordinates, radium, and plane
failure line segment coordinates are all
highlighted in the output listing, along
with the critical differential settlements,
liquefaction potential, and critical exit
gradient. If an analysis was not run, such
is indicated in a summary table at the
end of the output listing.
Software Support
Software support for CARDS consists
of a combined Handbook/User's Manual.
The Handbook section is intended to give
the user sufficient background to under-
stand the basic principle underlying the
various analyses being performed. A
separate chapter is devoted to each
analysis included in the program. After a
brief introduction stating the purpose of
the analysis, explaining when the analysis
should be used, and listing the capabilities
and limitations of the program, a section
of the basic theory and the method of
solution of the program are presented.
Following this, a complete step-by-step
long hand example solution is given. To
provide continuity, the same dike section
is used for all analyses. A complete
computer solution of the analysis of the
dike section is presented in the User's
Manual section for comparison.
The User's Manual section includes a
discussion of the capabilities, limitations,
ind essential details of each of the dif-
ferent blocks is presented, along with a
complete interactive example for the user
study. A sketch of the example section
and all required data are provided, along
with a summary output listing for the
example section. Block flow charts, a
program listing, and other pertinent
materials are appended to the Hand-
books/User's Manual.
The full report was submitted in ful-
fillment of Contract No. 68-03-3183,
Work Assignment No. 19 by the Univer-
sity of Cincinnati under the sponsorship
of the U.S. Environmental Protection
Agency.
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R. M. McCandless, A. Bodocsi, and P. R. Cluxton are with the University of
Cincinnati, Cincinnati, OH 45221.
Douglas Ammon is the EPA Project Officer (see below).
The complete report consists of paper copy and 4 computer diskettes, entitled
"Geotechnical Analysis for Review of Dike Stability (CARDS)"
Paper copy (Order No. PB 87-130 951/AS; Cost: $18.95)
Computer diskettes (Order No. PB 87-130 969/AS; Cost: $125.00)
The above items will be available only from: (costs subject to change)
National Technical Information Service
5285 Port Royal Road
Springfield. VA 22161
Telephone: 703-487-4650
The EPA Project Officer can be contacted at:
Hazardous Waste Engineering Research Laboratory
U.S. Environmental Protection Agency
Cincinnati, OH 45268
United States
Environmental Protection
Agency
Center for Environmental Research
Information
Cincinnati OH 45268
~'-'3l' [ "*? . nriCTAi
I ii.iAr,-f OSTAGE &
Official Business
Penalty for Private Use $300
EPA/600/S2-86/109
000032
^0604
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