Slope Stability and Earthmoving

Note: reference is made by several documents in this page to programs developed by the U.S. Army Corps of Engineers. These cannot be downloaded from this site; however, they are available here.

Construction Excavations and Reinforced Embankments on Soft Ground

Tuncer B. Edil
University of Wisconsin at Madison

In general , sides of construction excavations may be (i) unsupported (vertical or sloped) or (ii) braced or structurally supported. The choice in the use of these approaches depends, among other factors, on excavation depth, available space around the excavation, soil conditions (type, strength , weight) , ground water conditions, presence of nearby buildings and temporary loads, durations for which excavation will be kept open, economics and safety requirements. Herein, we will discuss only the salient aspects of those unsupported excavations or so-called open cuts. The forces which tend to cause caving or gross distortion and settlement of the side of an excavation include: (i) gravity in the form of the weight of the soil mass including soil-water , (ii) water pressures (seepage forces) , (iii) external loads (buildings, snow, water, excavation equipment, piled materials , etc.) , and (iv) vibrations (blasting, earthquakes, etc.). Resistance to caving is provided in open excavations primarily by the shearing resistance of the soil. In those cases where the shearing resistance offered by the soil is not adequate for safe excavation, structural support in terms of sheeting, shoring, bracing, and tie-back systems is provided. Conversely, shearing resistance can be increased by ground freezing or dewatering. Since the failure of open cut results only when shear failure has occurred at enough points to define a surface along which movement can take place, basic principles that govern the shear strength of soil must be clearly understood.

Design and Construction of Shale Embankments: Summary

April 1980

Guidelines for the use of shales in new construction, evaluation of existing embankments, and remedial treatment of distressed shale embankments are briefly described in this summary report.

Construction of the modern highway system has required large , high embankments using economically available fill from adjacent cuts or nearby borrow sources. Because of their widespread occurrence, shales and other weak, fine-grained sedimentary rock (siltstone, claystone, mudstone, etc.) were the main source of fill for many embankments from the Appalachian region to the Pacific Coast.

Earthmoving Operations

We also have the previous version of this document, FM 5-434, 15 June 2000

TM 3-34.62 (FM 5-434/15 June 2000)/MCRP 3-17.7I
June 2012

This is a guide for engineer personnel responsible for planning, designing, and constructing earthworks in the theatre of operations. It gives estimated production rates, characteristics, operation techniques, and soil considerations for earthmoving equipment. This guide should be used to help select the most economical and effective equipment for each individual operation.

This manual discusses the complete process of estimating equipment production rates. However, users of this manual are encouraged to use their experience and data from other projects in estimating production rates. The material in this manual applies to all construction equipment regardless of make or model. The equipment used in this manual are examples only. Information for production calculations should be obtained from the operator and maintenance manuals for the make and model of the equipment being used.

EMBANK: A Microcomputer Program to Determine One-Dimensional Compression Settlement Due to Embankment Loads

The EMBANK computer program itself can be downloaded here.

Dr. Alfredo Urzua
May 1993

The objective of this report is to introduce a microcomputer program for computing one-dimensional compression vertical settlement due to embankment loads. The program follows the equations presented by Lambe & Whitman (1969), Ladd (1973), and Poulos & Davis (1974). For the case of a strip symmetrical vertical embankment loading, the program superimposes two vertical embanknent loads. For the increment of vertical stresses at end of fill, the program internally superimpose a series of 10 rectangular loads to create the end-of-fill condition. The report presents the equations and analytical procedures utilized by the program and examples of the capabilities of the user-friendly data entry form. The computer program is coded in the Turbo Pascal 4.0 language and takes full advantage of the stand-alone, (single-user) characteristics of the IBM-PC through the use of “friendly” input menus and data-checking routines.

The code implements copyrighted portions of the microcomputer programs SAF-I and STRESS developed by PROTOTYPE Engineering, Inc., Winchester, MA, and uses the screen editor Turbo Magic From Sophisticated Software.

An Engineering Manual for Slope Stability Studies

J.M. Duncan, A.L. Buchignani and M. de Wet
Virginia Polytechnic University
March 1987

The purpose of this manual is to provide a simple, practical guide for slope stability studies. It is concerned with (1) the characteristics and critical aspects of various types of slope stability problems, (2) geologic studies and site investigation procedures, (3) methods of designing slopes, including field observations and experience, slope stability charts, and detailed analyses, (4) factors of safety, and (5) methods of stabilizing slopes and slides. The emphasis of this manual is on simple, routine procedures. It does not include advanced analysis procedures, nor does it deal with specialized problems such as design of dams or the stability of slopes during earthquakes. References are given to the sources of the material contained in the manual, and to more advanced procedures where appropriate, to provide avenues for studies going beyond the scope of this manual.

Evaluation of Slope Stability for Waste Rock Dumps in a Mine

Charanpreet Singh Flora
National Institute of Technology, Rourkela

The growing needs have been pushing the limits, to which the mining industry has to reach to lift itself to fulfil the demand. The effect can be seen from the methods of mining that have evolved over the years. The heavy machinery adopted for the extraction has been producing wastes in the form of waste rocks whose management is again of prime importance. The issues relating to the stability of these overburden dumps is catching attention worldwide from quite some time, which is quite important for the safe working in and around these monstrous structures as well as restricted availability of land. This paper deals with the stability issues of dumped slopes for a local chromite mine. The analysis cover analysis of various sections of the waste dumps from the mine including material properties, strength values, bench height and angle.

Prediction of Embankment Settlement Over Soft Soils

Vipulanandan, C., Bilgin, Ö., Y Jeannot Ahossin Guezo, Vembu, K.
and Erten, M. B.
December 2008

The objective of this project was to review and verify the current design procedures used by TxDOT to estimate the total and rate of consolidation settlement in embankments constructed on soft soils. Methods to improve the settlement predictions were identified and verified by monitoring the settlements in two highway embankments over a period of 20 months. Over 40 consolidation tests were performed to quantify the parameters that influenced the consolidation properties of the soft clay soils. Since there is a hysteresis loop during the unloading and reloading of the soft CH clays during the consolidation test, three recompression indices (Cr1, Cr2, Cr3) have been identified with a recommendation to use the recompression index Cr1 (based on stress level) to determine the settlement up to the preconsolidation pressure. Based on the laboratory tests and analyses of the results, the consolidation parameters for soft soils were all stress dependent. Hence, when selecting representative parameters for determining the total and rate of settlement, expected stress increases in the ground should be considered. Also the 1-D consolidation theory predicted continuous consolidation settlement in both of the embankments investigated. The predicted consolidation settlements were comparable to the consolidation settlement measured in the field. Constant Rate of Strain test can be used to determine the consolidation parameters of the soft clay soils. The effect of Active Zone must be considered in designing the edges of the embankments and the retaining walls.

Reliability Analysis and Risk Assessment for Seepage and Slope Stability Failure Modes for Embankment Dams

U.S. Army ETL 1110-2-561
31 January 2006

This document provides guidance for performance of risk assessment analyses of dam safety related detrimental seepage (internal erosion, piping, under seepage, and heave) and slope stability problems. Detailed descriptions of reliability and risk analysis for seepage and slope stability problems are provided.

Risk assessment is performed to evaluate various parameters to assist in the decision making process. A risk analysis and assessment provides the total annualized consequences or risk with and without the proposed seepage/stability correction project. By comparing the with and without projects, the risk assessment process is used to guide the selection of the alternative that is most effective in reducing the risk of unsatisfactory performance.

Site characteristics and potential modes of failure are identified. An event tree is then used to describe the various modes of unsatisfactory performance, and weighted damages are determined by multiplying the probabilities of occurrence and the costs incurred to give expected risk. Once the risk is determined for the without-project condition, the process is repeated for each with-project alternative. The most feasible alternative can then be selected.

Reliability and Stability Assessment
of Concrete Gravity Structures (RCSLIDE):
Theoretical Manual

Bilal M. Ayyub, Ru-Jen Chao, BMA Engineering, Inc.
Robert C. Patev, Mary Ann Leggett, WES
US Army Corps of Engineers Technical Report ITL-98-6
December 1998

Current safety analysis procedures and computer programs such as CSLIDE (Pace and Noddin 1987) for concrete retaining walls and gravity structures compute traditional safety factors that are not based on reliability analysis. CSLIDE defines the safety factor as the ratio of sliding resistance to sliding force. Safety factors are not accurate measures of stability reliability because they do not account for the various uncertainties in underlying parameters or variables of stability problems. Also, the factors of safety do not convey the nonlinear nature of relationships between the margin of safety that they measure and the unsatisfactory performance likelihood that can be used as a basis for measuring stability reliability.

The objective of this study was to develop reliability assessment methods for the stability of gravity concrete structures. This report describes the probability-based reliability assessment methodology for concrete retaining walls and gravity structures that was developed. The methodology is based on the U.S. Army Corps of Engineers Computer-Aided Structural Engineering (CASE) program for Sliding Stability of Concrete Structures (CSLIDE, Pace and Noddin 1987). A user interface for CSLIDE and the reliability program based on CSLIDE (called RCSLIDE) was also developed using Microsoft Visual Basic. The significance of the software development procedure described in this study is that is establishes prototype reliability software that is modular and based on an existing CASE program. Other CASE programs can be modified and utilized for reliability purposes in a similar fashion.

The development of the methodology required the definition of a performance function for retaining walls and gravity structures, development of a library of probability functions (Ayyub and Chao 1994), development of a structural reliability assessment module, development of user interfaces, and selection and performance of test cases.

Road Embankment and Slope Stabilization

Dr. Mohamed Ashour and Mr. Hamed Ardalan
UTCA Final Report Number 09305
31 July 2010

This report and the accompanying software are part of efforts to improve the characterization and analysis of pile-stabilized slopes using one or two rows of driven piles. A combination of the limit equilibrium analysis and strain wedge (SW) model technique is employed to assess the stability of vulnerable slopes before and after using driven piles to improve the slope stability. This report focuses on the entry of input data, interpretation of the output results, and description of the employed technique. In addition to a comparison study with a full-scale load test, the finite element (FE) analysis using a general-purpose FE package, “PLAXIS,” is performed to verify the results. The characterization of lateral load induced by slipping mass of soils can be accomplished using the modified SW model technique. The SW model for laterally loaded pile behavior is a new predictive method (recommended as an alternative method by AASHTO [2007]) that relates the stress-strain behaviour of soil in the developing three-dimensional passive wedge in front of the pile (denoted as the strain wedge) under lateral load to the one-dimensional beam-on-elastic foundation parameters. Two failure scenarios are employed in the developed computer program to include pile stabilization for 1) existing slip surface of failed slope and 2) potential failure surface. The two scenarios evaluate the distribution of the soil driving forces with the consideration of the soil flow-around failure, soil strength, and pile spacing. The developed procedure can also account for the external pile head lateral load and moment along with the driving force induced by the sliding mass of soil. The developed computer program is a design tool in which the designer can select an economic pile size to stabilize slopes. In addition to the external lateral loads applied at the pile head, the presented research work determines the mobilized driving force caused by sliding mass of soil that needs to be transferred via installed piles to stable soil layers below the slip surface. The side and front interaction between piles and sliding mass of soil is one of the main features of this project. The work presented also evaluates the appropriate pile spacing between the piles in the same pile row (wall) and the spacing between the pile rows. The computer program provides a flexible graphical user interface that facilitates entering data and analysing/plotting the results. The finite element analysis (using PLAXIS) was used to investigate the results. A field test for pile-stabilized slope is used to validate the results obtained from the finite element analysis and the developed technique.<

Slope Maintenance and Slide Restoration

Tommy C. Hopkins, David L. Allen, Robert C. Deen and Calvin G. Grayson
FH WA-RT-88-040
December 1988

Each year U.S. highway agencies spend millions of dollars in maintaining highway embankments, slopes, and other earth structures as well as removing rock falls and soil debris from roadways and repairing landslides. Activities from maintaining highway slopes and restoring landslides often cause traffic slow dawn and stoppage that creates serious safety hazards and consumes significant highway maintenance and construction funds. In addition, economic losses due to the inconvenience to the travelling public is often immeasurable.

During 1984 and 1985, as part of a continuing project to evaluate and improve maintenance activities, a study on slope maintenance and slide restoration was undertaken by the Federal Highway Administration (FHWA), Office of Implementation. This joint effort by engineers from the FHWA and six state highway agencies (that is, California, Kentucky, Oregon, Pennsylvania, Texas, and Wyoming) developed guidelines for slope maintenance and slide restoration. These guidelines reflect the collective experience of the six state highway agencies and are documented in FHWA report (TS-85-231) entitled “Guidelines for Slope Maintenance and Slide Restoration.”

This technical note was developed and based on the above report for use by Technology Transfer Centres funded through the Rural Technical Assistance Program of the Federal Highway Administration in conducting training of the subject title.

This manual represents one of the many contributions of Dr. Robert C. Deen to the transportation research , and education community. Dr. Deen died on March 25, 1988, while completing the editing of this manual.

Slope Stability

Engineer Manual EM 1110-2-1902
31 October 2003

This engineer manual provides guidance for analysing the static stability of slopes of earth and rock-fill dams, slopes of other types of embankments, evacuated slopes, and natural slopes in soil and soft rock. Methods for analysis of slope stability are described and are illustrated by examples in the appendices. Criteria are presented for strength tests, analysis conditions, and factors of safety. The criteria in this manual are to be used with methods of stability analysis that satisfy all conditions of equilibrium. Methods that do not satisfy all conditions of equilibrium may involve significant inaccuracies and should only be used under the restricted conditions described herein.

Stress Distribution Within and Under Long Elastic Embankments

W.H. Perloff, G.Y. Baladi and M.E. Harr
Joint Highway Research Project #14
June 1967

The distribution of stresses within and under long elastic embankments continuous with the underlying material is presented. The magnitude and distribution of stress in the foundation material in the vicinity of the embankment is significantly different from that predicted by the usual assumption of stress proportional to embankment height applied normal to the foundation. Influence charts for a variety of embankment shapes are given.

User’s Guide: UTEXAS2 Slope-Stability Package; Volume I, User’s Manual

Edris, Jr., Earl V. Wright, Stephen G.
US Army Corps of Engineers
Instruction Report GL-87-1
August 1987

This report is the user’s guide volume of the UTEXAS2 (University of Texas Analysis of Slopes – version 2) slope-stability package. This package describes a slope-stability program which can calculate the factor of safety by Spencer’s method, simplified Bishop’s procedure, force equilibrium procedure with Corps of Engineers Modified Swedish side-force assumption of parallel side forces at a user-specified inclination and force equilibrium procedure with Lowe and Karafiath’s side force assumptions. The program will calculate the safety factor for either a prescribed shear surface or for a search of the critical shear surface. Both circular and noncircular shear surfaces can be evaluated. There are five options for the type of shear strength data and six options for specifying pore pressures. All analysis procedures and major features can be run in a single data file which is free- field format and utilizes command words. Graphics capability for displaying the input data and the final shear surface is available. Special capabilities include “pseudo-static” seismic analysis, slope reinforcement, curved (multi-linear) shear strength envelope, anisotropic shear strength, and the ability to have multiple plezometrlc lines.

Vertical Stresses Beneath Embankment and Footing Loadings

U.S. Army Corps of Engineers
March 1968

The program computes the vertical stresses induced in a semi
inifinite mass by a group of uniformly loaded rectangular areas. Under one program option the vertical foundation stresses caused by an embankment loading are approximated by assuming that the embankment is composed of a series of uniformly loaded rectangular areas lying on the top of one another. The program can handle up to 100 footing loads. The vertical stresses may be calculated by either Boussinesq or Westergaard solutions for vertical stresses.