The Hepburn landslide: an interactive slope-stability and seepage analysis

1991 ◽  
Vol 28 (4) ◽  
pp. 556-573 ◽  
Author(s):  
G. A. Misfeldt ◽  
E. Karl Sauer ◽  
E. A. Christiansen
Keyword(s):  
Factor Of Safety ◽  
Slope Failure ◽  
Slip Surface ◽  
Friction Angle ◽  
Seepage Analysis ◽  
Continuous Processes ◽  
Valley Slope ◽  
Slip Surfaces ◽  
Artesian Aquifer ◽  
Saline Springs

Mechanisms of active landslides are continuous processes involving the dynamics of slope failure interacting with the groundwater regime. This process is simulated in phases by combining stability calculations interactively with a seepage analysis to determine the factor of safety for a dormant landslide near Hepburn, Saskatchewan. The landslide is a multiple retrogressive failure with two parallel slip surfaces at different elevations. The slip surfaces are in originally overconsolidated Cretaceous and Tertiary clays softened by shear from glaciation. An artesian aquifer is present at the base of the slip surface, causing saline springs at the base of the valley slope. A residual effective friction angle of 6.7° with zero cohesion was found to best characterize the shear strength of the clays in the failure zone. Potential nets and head profiles from the seepage analysis illustrate the strong influence of changing topography on the groundwater flow system. The present-day factor of safety for the dormant landslide was estimated to be 1.10. Key words: multiple retrogressive landslides, dormant landslide, seepage modelling, residual strength, artesian conditions, glacial drift, Cretaceous clays.

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.

Potential Slip Surfaces of Slope with Strength Parameters

2011 ◽  
Vol 243-249 ◽  
pp. 3315-3318 ◽  
Author(s):  
Hang Lin ◽  
Ping Cao
Keyword(s):  
Shear Strength ◽  
Numerical Analysis ◽  
Factor Of Safety ◽  
Slip Surface ◽  
Friction Angle ◽  
Shear Strength Parameters ◽  
Strength Parameters ◽  
Slip Surfaces ◽  
Stability Of Slope ◽  
The Stability

The cohesion c and friction angle φ are the main strength parameters influencing the stability of slope. Any of them changes, the factor of safety of slope will change, but it has seldom been considered in the literature how the potential slip surface will change at the same time. In the present paper, the analytical deduction and numerical analysis are done to find out the effect of shear strength parameters c and φ to the distribution of potential slip surface. The study shows that, the potential slip surface is affected by the combination of c and φ, whose function is λ=c/(γhtanφ).

Simulation of risk of progressive slope failure

1992 ◽  
Vol 29 (1) ◽  
pp. 94-102 ◽  
Author(s):  
R. N. Chowdhury
Keyword(s):  
Shear Strength ◽  
Slope Failure ◽  
Direct Evidence ◽  
Slip Surface ◽  
Progressive Failure ◽  
Residual Shear Strength ◽  
Slip Surfaces ◽  
Surface Measurements ◽  
Risk Simulation ◽  
Deterministic And Probabilistic Approaches

Understanding of progressive failure of slopes is of immense interest to geotechnical engineers and others concerned with the occurrence of landslides. One important aspect of research is the development of relevant analytical and numerical techniques. Both deterministic and probabilistic approaches can be used to study the development of progressive failure, provided valid geomechanics models form the basis of such studies. In this paper the risk of failure is simulated within a probabilistic framework. Of particular interest is the increase in the probability of failure, as overstress (and consequent localized failure) is considered to have actually occurred over an increasing proportion of a slip surface within the slope. The perception or interpretation of local failure is often based on observational data from surface measurements and subsurface instrumentation. Knowledge of spatial progression of failure may similarly be based on indirect and direct evidence. In the proposed simulation process the peak and residual shear strength of the slope material are regarded as one-dimensional random fields, and therefore spatial variability of each parameter is taken into consideration. Key words : analysis, clays, failure, shear strength, slopes, stability, landslides, probabilistic analysis, reliability analysis, progressive failure, slip surfaces, risk simulation, statistical analysis.

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.

Analysis of Slope Failure Mechanisms Considering Micropile-Soil Interaction

2013 ◽  
Vol 535-536 ◽  
pp. 565-568 ◽  
Author(s):  
Hong Jian Liao ◽  
Cheng Lin Tian ◽  
Hang Zhou Li
Keyword(s):  
Large Scale ◽  
Slope Failure ◽  
Slip Surface ◽  
Loess Soil ◽  
Scale Model ◽  
Maximum Shear Strain ◽  
Loess Slope ◽  
Slip Surfaces ◽  
Large Scale Model ◽  
Stress And Deformation

A large scale model test was carried out in loess slope, in which the stress and deformation characteristics of slopes reinforced with different arrangements of micropiles were studied. The mechanism of the micropile-soil interaction and the reinforcement effect of micropiles in loess slope were analysed. Based on the scale of in-situ loess slope and the physical mechanics parameters of loess soil, a numerical model was established by using finite difference method. For a reasonable arrangement of micropiles in step-shaped slope, the critical slip surfaces were determined considering the influence of slope inclination, ratio of step height and loading position. The micropiles were arranged in the step-shaped slope based on the critical slip surface, and the relationship between the ultimate bearing capacity of slope and shear strength parameters of loess soil was studied. The maximum shear strain of micropile-soil and moment of micropiles were calculated, and then the mechanism of the micropile-soil interaction was analysed.

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.

Stabilization of the Highway Slope using Recycled Plastic Pins

2021 ◽  
pp. 036119812110071
Author(s):  
Mohammad Sadik Khan ◽  
MD Sahadat Hossain ◽  
Masoud Nobahar
Keyword(s):  
Finite Element ◽  
Factor Of Safety ◽  
Performance Monitoring ◽  
Slope Failure ◽  
Slip Surface ◽  
Design Method ◽  
Biological Degradation ◽  
Element Analysis ◽  
Rain Gauges ◽  
Recycled Plastics

The recycled plastic pin (RPP) is made from recycled plastics and waste materials (i.e., polymer, sawdust, fly ash, etc.). It is a lightweight material and is less susceptible to chemical and biological degradation than the alternative reinforcing element. RPPs are driven into the slope face and provide additional resistance along the slip surface which increases the factor of safety against shallow slope failure. The current paper summarizes a case study using RPPs to repair highway slopes, investigating the use of a finite element method, and summarizes a design method. The highway slope was located over US 287 near the St. Paul overpass in Midlothian, Texas. The surficial movement had taken place over the slope, resulting in cracks over the shoulder near the bridge abutment. Three 15.2-m sections over the slope were reinforced using RPPs. After RPP installation, the slope was instrumented with inclinometers, rain gauges, moisture sensors, and water potential probes, and was monitored periodically. The performance monitoring results indicated that RPP provides resistance in the slope constructed using highly plastic clay. Further analysis of the slope using finite element analysis indicates that RPP can significantly improve the marginal slopes to a factor of safety more than 2.0. Finally, a simple design chart is presented to calculate the capacity of RPPs for slope repair design using an infinite slope approach.

scholarly journals Slip surface in narrow backfill behind retaining wall

2021 ◽  
Vol 331 ◽  
pp. 03012
Author(s):  
Abdul Hakam ◽  
Deni Irda Mazni
Keyword(s):  
Factor Of Safety ◽  
Slope Failure ◽  
Slip Surface ◽  
Retaining Wall ◽  
Soil Mass ◽  
Soil Slope ◽  
Soil Pressure ◽  
Earth Reinforcement ◽  
The Stability ◽  
Steep Slopes

For a particular area in Geotechnical engineering, a soil slope is defined as a surface of soil mass which is inclined. It the slope is unstable or has insufficient factor of safety, then it needs to be strengthened by a retaining wall or a particular earth reinforcement to ensue slope failure does not occur. It has long been known that the pattern of slip failure is classified into two main types: translation and rotation. Other patterns of slip failure can be approached within the two mentioned types above. The main purpose of this classification is to assist the engineers in the process of the the stability analysis in purpose to obtain the safety factor of the slope and the reinforcement system if any. For the retaining wall reinforcement analysis, the developed method is generally in the form of soil pressure behind the wall. The pressure due to the self weight of the soil is generated by assuming the backfill is long enough, so that the slip failure can be fully described according to the two main types above. Then in cases where the backfill behind the wall is quite narrow, the method should be corrected or modified. These narrow areas are often found on roads that are built on relatively steep slopes. In this paper, the form of the slip failure behind a narrow retaining wall is presented. The results of this study are very useful for developing analytical methods for retaining soils that are built in narrow areas due to location limitations.

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.

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.

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