Effect of the axis of moment equilibrium in slope stability analysis

1992 ◽  
Vol 29 (3) ◽  
pp. 456-465 ◽  
Author(s):  
D. G. Fredlund ◽  
Z. M. Zhang ◽  
L. Lam
Keyword(s):  
Slope Stability ◽  
Factor Of Safety ◽  
Slip Surface ◽  
Limit Equilibrium ◽  
Stability Limit ◽  
Slip Surfaces ◽  
Moment Equilibrium ◽  
Simplified Method ◽  
General Limit ◽  
The Moment

Some of the methods of slices satisfying moment equilibrium derived for circular slip surfaces have been extended to accommodate noncircular (or composite) type slip surfaces. A question arises regarding the point about which moment equilibrium should be taken and whether varying the center for moment equilibrium has a significant effect upon the computed factor of safety. This paper addresses the question of the effect of the center for moment equilibrium as it pertains to noncircular (or composite) slip surfaces. In particular, extensions of the Ordinary, Bishop's simplified, and the General Limit Equilibrium (GLE) methods are examined. The results show that considerable variations in the factor of safety can occur when using the extended Ordinary method. The extended Bishop's simplified method shows varying factors of safety as the moment axis moves vertically. Variations in the computed factor of safety can generally be expected to be less than 12%. The GLE, Morgerstern–Price, and Spencer methods are independent of the axis for moment equilibrium. Key words : slope stability, limit equilibrium, moment equilibrium, factor of safety, noncircular slip surface.

Convergence aspect of limit equilibrium methods for slopes

1990 ◽  
Vol 27 (1) ◽  
pp. 145-151 ◽  
Author(s):  
R. N. Chowdhury ◽  
S. Zhang
Keyword(s):  
Factor Of Safety ◽  
Slip Surface ◽  
Limit Equilibrium ◽  
Solution Process ◽  
Iterative Solution ◽  
Friction Angle ◽  
Equilibrium Analysis ◽  
Negative Slope ◽  
Slip Surfaces ◽  
Geological Discontinuity

This note is concerned with the multiplicity of solutions for the factor of safety that may be obtained on the basis of the method of slices. Discontinuities in the function for the factor of safety are discussed and the reasons for false convergence in any iterative solution process are explored, with particular reference to the well-known Bishop simplified method (circular slip surfaces) and Janbu simplified or generalized method (slip surfaces of arbitrary shape). The note emphasizes that both the solution method and the method of searching for the critical slip surface must be considered in assessing the potential for numerical difficulties and false convergence. Direct search methods for optimization (e.g., the simplex reflection method) appear to be superior to the grid search or repeated trial methods in this respect. To avoid false convergence, the initially assumed value of factor of safety F0 should be greater than β1(=−tan α1 tan [Formula: see text]) where α1 and [Formula: see text] are respectively the base inclination and internal friction angle of the first slice near the toe of a slope, the slice with the largest negative reverse inclination. A value of F0 = 1 + β1, is recommended on the basis of experience. If there is no slice with a negative slope for any of the slip surfaces generated in the automatic, search process, then any positive value of F0 will lead to true convergence for F. It is necessary to emphasize that no slip surface needs to be rejected for computational reasons except for Sarma's methods and similarly no artificial changes need to be made to the value of [Formula: see text] except for Sarma's methods. Key words: slope stability, convergence, limit equilibrium, analysis, optimization, slip surfaces, geological discontinuity, simplex reflection technique.

Some difficulties associated with the limit equilibrium method of slices

1983 ◽  
Vol 20 (4) ◽  
pp. 661-672 ◽  
Author(s):  
R. K. H. Ching ◽  
D. G. Fredlund
Keyword(s):  
Slope Stability ◽  
Factor Of Safety ◽  
Limit Equilibrium ◽  
Stability Limit ◽  
Limit Equilibrium Method ◽  
Soil Conditions ◽  
Side Force ◽  
Limit Equilibrium Methods ◽  
Equilibrium Method ◽  
The Stability

Several commonly encountered problems associated with the limit equilibrium methods of slices are discussed. These problems are primarily related to the assumptions used to render the inherently indeterminate analysis determinate. When these problems occur in the stability computations, unreasonable solutions are often obtained. It appears that problems occur mainly in situations where the assumption to render the analysis determinate seriously departs from realistic soil conditions. These problems should not, in general, discourage the use of the method of slices. Example problems are presented to illustrate these difficulties and suggestions are proposed to resolve these problems. Keywords: slope stability, limit equilibrium, method of slices, factor of safety, side force function.

A method for locating critical slip surfaces in slope stability analysis

2001 ◽  
Vol 38 (2) ◽  
pp. 328-337 ◽  
Author(s):  
Da-Yong Zhu
Keyword(s):  
Stability Analysis ◽  
Slope Stability ◽  
Factor Of Safety ◽  
High Efficiency ◽  
Slip Surface ◽  
Numerical Procedure ◽  
Slope Stability Analysis ◽  
Case Examples ◽  
Slip Surfaces ◽  
Global And Local

This paper presents a new method for locating critical slip surfaces of general shapes in slope stability analysis. On the basis of the principle of optimality, along with the method of slices, a critical slip field (CSF) in a slope is postulated which consists of a family of slip surfaces having maximum values of unbalanced thrust forces at exit points on the slope face. A numerical procedure is developed for constructing the CSF. The critical slip surface having minimum factor of safety is included in the CSF. All the critical slip surfaces corresponding to all of the exit points are thus determined consecutively, resulting in a global critical slip field (GCSF) which exhibits both global and local slope stability. Comparisons with other methods are made which indicate the high efficiency and accuracy of the proposed approach. Applications of the proposed method to two case examples are given, the results of which demonstrate its applicability to practical engineering.Key words: slope, stability, analysis, factor of safety, critical slip field.

Search for critical slip surfaces based on finite element method

1995 ◽  
Vol 32 (2) ◽  
pp. 233-246 ◽  
Author(s):  
Jin-Zhang Zou ◽  
David J. Williams ◽  
Wen-Lin Xiong
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Dynamic Programming ◽  
Factor Of Safety ◽  
Slip Surface ◽  
Limit Equilibrium ◽  
Dynamic Programming Method ◽  
Critical Slip Surface ◽  
Slip Surfaces ◽  
Element Method

In this paper, finite element methods (FEM) are used to determine local shear strength mobilization ratios within a slope and to indicate the probable location of the critical slip surface. To locate the critical slip surface and hence determine the minimum factor of safety, an improved dynamic programming method (IDPM) is employed, in which possible slip surfaces, which must pass between state points, may pass both between and along stages. The IDPM is coupled with an expression for the factor of safety for which the stresses are obtained from the FEM. The results obtained using the FEM–IDPM, for a homogeneous slope and for a test embankment on soft Bangkok clay, have been compared with those observed and obtained using the traditional finite element method and the generalized limit equilibrium wedge method. The FEM–IDPM has the advantage over limit equilibrium methods that the strain- and time-dependent behaviour of soil and the staged construction of the slope can be modelled. Key words : critical slip surface, dynamic programming, factor of safety, finite element method, limit equilibrium method, slope stability.

scholarly journals Numerical Computation of Homogeneous Slope Stability

2015 ◽  
Vol 2015 ◽  
pp. 1-10 ◽  
Author(s):  
Shuangshuang Xiao ◽  
Kemin Li ◽  
Xiaohua Ding ◽  
Tong Liu
Keyword(s):  
Slope Stability ◽  
High Efficiency ◽  
Slip Surface ◽  
Limit Equilibrium ◽  
Computation Time ◽  
Computational Accuracy ◽  
Slope Analysis ◽  
Slip Surfaces ◽  
Simple Slope ◽  
Computation Error

To simplify the computational process of homogeneous slope stability, improve computational accuracy, and find multiple potential slip surfaces of a complex geometric slope, this study utilized the limit equilibrium method to derive expression equations of overall and partial factors of safety. This study transformed the solution of the minimum factor of safety (FOS) to solving of a constrained nonlinear programming problem and applied an exhaustive method (EM) and particle swarm optimization algorithm (PSO) to this problem. In simple slope examples, the computational results using an EM and PSO were close to those obtained using other methods. Compared to the EM, the PSO had a small computation error and a significantly shorter computation time. As a result, the PSO could precisely calculate the slope FOS with high efficiency. The example of the multistage slope analysis indicated that this slope had two potential slip surfaces. The factors of safety were 1.1182 and 1.1560, respectively. The differences between these and the minimum FOS (1.0759) were small, but the positions of the slip surfaces were completely different than the critical slip surface (CSS).

A 3D slope stability analysis method assuming parallel lines of intersection and differential straining of block contacts

2002 ◽  
Vol 39 (4) ◽  
pp. 799-811 ◽  
Author(s):  
Muhsiung Chang
Keyword(s):  
Slope Stability ◽  
Factor Of Safety ◽  
Slip Surface ◽  
Limit Equilibrium ◽  
Three Dimensional ◽  
Shear Stresses ◽  
Block System ◽  
Stability Of Slopes ◽  
Sliding Mechanism ◽  
The Stability

A three-dimensional (3D) method of analysis of the stability of slopes was developed based on the sliding mechanism observed in the 1988 failure of the Kettleman Hills landfill slope (Kettleman City, California) and the associated model studies. By adopting a limit equilibrium concept, the method assumes the sliding mass as a block system in which the contacts between blocks are inclined. The lines of intersection of the block contacts are assumed to be parallel, which enables the sliding kinematics. In consideration of the differential straining between blocks, the shear stresses on the slip surface and the block contacts are evaluated based on the degree of shear strength mobilization on these contacts. The overall factor of safety is calculated based on the force equilibrium of the individual blocks and the entire block system as well. Based on comparisons with a series of hypothetical 3D and 2D problems with known solutions, the method was generally found to be accurate in predicting the stability of slopes involving a translational type of sliding failure. For rotational sliding failures in clays, however, the method appears to slightly overestimate the calculated factor of safety; up to as much as 10% in a typical problem examined in this study.Key words: slope stability, 3D method, limit equilibrium, block kinematics, strain incompatibility.

scholarly journals Slope Stability Analysis to Correlate Shear Strength with Slope Angle and Shear Stress by Considering Saturated and Unsaturated Seismic Conditions

2021 ◽  
Vol 11 (10) ◽  
pp. 4568
Author(s):  
Muhammad Israr Khan ◽  
Shuhong Wang
Keyword(s):  
Shear Stress ◽  
Shear Strength ◽  
Stability Analysis ◽  
Slope Stability ◽  
Factor Of Safety ◽  
Slip Surface ◽  
Limit Equilibrium ◽  
Slope Angle ◽  
Slope Stability Analysis ◽  
Soil Slope

Assessment and analysis of soil slope stability is an important part of geotechnical engineering at all times. This paper examines the assessment of soil slope stability in fine-grained soils. The effect of change in shear strength (τ), shear stress (σ) and slope angle (β) on the factor of safety has been studied. It correlates shear strength with slope angle and shear stress by considering the horizontal seismic coefficients in both saturated and unsaturated conditions. The slope failure surface was considered a circular slip surface. Statistical package for social sciences (SPSS) and Slide, numerical modeling software and limit equilibrium slope stability analysis software, respectively, are used to find out the correlations between the three basic parameters. The slope angle varied from 70 to 88 degrees, which are the most critical values for slope angles, and a total of 200 analyses were performed. τ, β and σ are correlated, and the correlations are provided in the results section. The results indicate that the correlations developed between the parameters have a very close relationship. The applicability of the developed equations is above 99%. These correlations are applicable in any type of soil slope stability analysis, where the value of shear strength and factor of safety is required with the variation of slope angle and shear stress.

Discussion of Evaluation Index in Probabilistic Slope Stability Analysis

2011 ◽  
Vol 90-93 ◽  
pp. 94-97
Author(s):  
Zhen Jun Wu ◽  
Wei Wang
Keyword(s):  
Stability Analysis ◽  
Slope Stability ◽  
Factor Of Safety ◽  
Slip Surface ◽  
Slope Stability Analysis ◽  
Evaluation Index ◽  
First Order ◽  
Slip Surfaces ◽  
Reliability Method ◽  
Probabilistic Slope Stability Analysis

Probabilistic slope stability analyses have been adopted in study and geotechnical practice. But there are many misconceptions in the literature. One of these is the evaluation index of slope. The evaluation index will not always have the same meanings for the different slip surfaces. There are five kinds of slip surfaces in probabilistic slope stability analysis: slip surface of minimum factor of safety at mean parameters, mix slip surfaces of minimum factor of safety during each iteration, slip surface of minimum reliability index, slip surface of minimum factor of safety at specific parameters combination and slip surface of minimum factor of safety during each iteration in first order reliability method. For different slip surfaces the evaluation indices may be different. The relation among these evaluation indices is discussed and the applicability of the evaluation index is suggested.

scholarly journals The Hydromechanical Interplay in the Simplified Three-Dimensional Limit Equilibrium Analyses of Unsaturated Slope Stability

Geosciences ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 73
Author(s):  
Panagiotis Sitarenios ◽  
Francesca Casini
Keyword(s):  
Analytical Solution ◽  
Slope Stability ◽  
Slope Failure ◽  
Failure Modes ◽  
Pore Water Pressure ◽  
Limit Equilibrium ◽  
Water Pressure ◽  
Three Dimensional ◽  
Stability Limit ◽  
Smooth Transition

This paper presents a three-dimensional slope stability limit equilibrium solution for translational planar failure modes. The proposed solution uses Bishop’s average skeleton stress combined with the Mohr–Coulomb failure criterion to describe soil strength evolution under unsaturated conditions while its formulation ensures a natural and smooth transition from the unsaturated to the saturated regime and vice versa. The proposed analytical solution is evaluated by comparing its predictions with the results of the Ruedlingen slope failure experiment. The comparison suggests that, despite its relative simplicity, the analytical solution can capture the experimentally observed behaviour well and highlights the importance of considering lateral resistance together with a realistic interplay between mechanical parameters (cohesion) and hydraulic (pore water pressure) conditions.

Slope Stability Analysis of Elastic Limit Equilibrium Method

2013 ◽  
Vol 275-277 ◽  
pp. 1423-1426
Author(s):  
Lin Kuang ◽  
Ai Zhong Lv ◽  
Yu Zhou
Keyword(s):  
Stability Analysis ◽  
Slope Stability ◽  
Safety Factor ◽  
Slip Surface ◽  
Limit Equilibrium ◽  
Limit Equilibrium Method ◽  
Slope Stability Analysis ◽  
Sliding Surface ◽  
Tangential Stresses ◽  
Equilibrium Method

Based on finite element analysis software ANSYS, slope stability analysis is carried out by Elastic limiting equilibrium method proposed in this paper. A series of sliding surface of the slope can be assumed firstly, and then stress field along the sliding surface is analyzed as the slope is in elastic state. The normal and tangential stresses along each sliding surface can be obtained, respectively. Then the safety factor for each slip surface can be calculated, the slip surface which the safety factor is smallest is the most dangerous sliding surface. This method is different from the previous limit equilibrium method. For the previous limit equilibrium method, the normal and tangential stresses along the sliding surface are calculated based on many assumptions. While, the limit equilibrium method proposed in this paper has fewer assumptions and clear physical meaning.

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