Influence of the groundwater on the stability of a clay bank in Baie James, Québec

1985 ◽  
Vol 22 (3) ◽  
pp. 409-413
Author(s):  
Peter Rosenberg ◽  
Jacques Provençal ◽  
Guy Lefebvre ◽  
J.-Jacques Paré
Keyword(s):  
Pore Pressure ◽  
Factor Of Safety ◽  
Field Measurements ◽  
Failure Surface ◽  
Surface Failure ◽  
Failure Morphology ◽  
Critical Failure Surface ◽  
Groundwater Regime ◽  
The Stability ◽  
River Banks

The Rivière Broadback in northern Québec flows westward almost parallel to latitude 51 °N to discharge into Baie James at its southern end. Near the estuary the river banks are in clay. Surveys of the landsliding activity showed that many of the slides are superficial, with depths seldom greater than about 2 m, and are usually in the clay crust.Instrumentation revealed regional groundwater pattern close to the river banks that showed areas varying from those with significant underdrainage to those with hydrostatic pressure conditions. The stability of 26 m high river slopes inclined at 27° in an area of underdrainage was investigated.Triaxial testing on undisturbed tube samples was used to obtain the postpeak parameters. Stability analyses gave a factor of safety close to one for shallow failure surfaces. With underdrainage, the factor of safety for deep failure surfaces is appreciably higher. When hydrostatic pore pressure conditions are assumed, analysis gave a factor of safety for deep failure that was reduced by about 30%.The results of the analyses emphasize the relation between the morphology of the landslide activity and the groundwater regime. With underdrainage, effective stresses increase much faster with depth and the critical failure surface is always close to the surface, as confirmed by field observations. Key words: natural slope, clay, pore pressure, field measurements, stability failure surface, failure morphology.

Finite element analysis of the stability of a vertical cut using an anisotropic soil model

1988 ◽  
Vol 25 (1) ◽  
pp. 119-127 ◽  
Author(s):  
P. K. Banerjee ◽  
A. S. Kumbhojkar ◽  
N. B. Yousif
Keyword(s):  
Finite Element ◽  
Pore Pressure ◽  
Factor Of Safety ◽  
Constitutive Relations ◽  
Field Measurements ◽  
Failure Surface ◽  
Time To Failure ◽  
Soil Behavior ◽  
Element Analysis ◽  
Anisotropic Soil

A finite element (FE) analysis of the field test excavation in Welland Clay is performed using an anisotropic soil behavior model. This paper describes the model, FE formulation, and transient effective stress stability analysis, and compares FE results with the field measurements. The analysis reflects the postexcavation decrease in the factor of safety with time and predicts the failure of the slope along the observed failure surface. The parametric study shows that the time to failure is a function of the pore pressure boundary conditions at the excavation surface and affects the transient factor of safety. Key words: constitutive relations, excavations, finite element, plasticity models, pore pressure, soil anisotropy, stability.

scholarly journals An Extension of Taylor’s φ-Circle Method and Some Stability Charts for Submerged Slopes

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Ping Li ◽  
Luanhua Dong ◽  
Xiaowen Gao ◽  
Tonglu Li ◽  
Xiaokun Hou
Keyword(s):  
Analytical Solutions ◽  
Factor Of Safety ◽  
Classical Method ◽  
Circle Method ◽  
Failure Surface ◽  
Underground Water ◽  
Submerged Condition ◽  
Stability Calculation ◽  
Critical Failure Surface ◽  
Underground Water Table

Taylor’s φ-circle method is a classical method for slope stability calculation, which has analytical solutions. Taylor derived equations in two cases separately, namely, (i) the outlet of the critical failure surface is at the slope toe and (ii) the outlet of the failure surfaces is not at the slope toe. The method is only appropriate for two conditions (without underground water table in slopes or totally submerged slopes). In this study, a general equation that unifies the equations of the two cases is proposed and partially submerged condition is introduced. The critical failure surfaces corresponding to the minimum factor of safety are determined using the computer program proposed by the authors. The general expression of the safety factor of slopes under the following four conditions is derived, namely, (i) partly submerged, (ii) completely submerged, (iii) water sudden drawdown, and (iv) water slow drawdown. The corresponding charts for practical use are available.

scholarly journals Failure Mechanism and Factor of Safety for Spatially Variable Undrained Soil Slope

2019 ◽  
Vol 2019 ◽  
pp. 1-17 ◽  
Author(s):  
Liang Li ◽  
Xuesong Chu
Keyword(s):  
Random Field ◽  
Failure Mechanism ◽  
Factor Of Safety ◽  
Limit Equilibrium ◽  
Vertical Direction ◽  
Failure Surface ◽  
Cohesive Soil ◽  
Soil Slope ◽  
The Stability ◽  
Undrained Soil

This paper aims to investigate the differences in factor of safety (FS) and failure mechanism (FM) for spatially variable undrained soil slope between using finite element method (FEM) , finite difference method (FDM), and limit equilibrium method (LEM). The undrained shear strength of cohesive soil slope is modeled by a one-dimensional random field in the vertical direction. The FS and FM for a specific realization of random field are determined by SRT embedded in FEM- and FDM-based software (e.g., Phase2 6.0 and FLAC) and LEM, respectively. The comparative study has demonstrated that the bishop method (with circular failure surface) exhibits performance as fairly good as that of SRT both in FS and FM for the undrained slope cases where no preferable controlling surfaces such as hydraulic tension crack and inclined weak seams dominate the failure mechanism. It is, however, worthwhile to point out that unconservative FM is provided by the Bishop method from the aspect of failure consequence (i.e., the failure consequence indicated by the FM from the Bishop method is smaller than that from SRT). The rigorous LEM (e.g., M-P and Spencer method with noncircular failure surface) is not recommended in the stability analysis of spatially variable soil slopes before the local minima and failure to converge issues are fully addressed. The SRT in combination with FEM and/or FDM provides a rigorous and powerful tool and is highly preferable for slope reliability of spatially variable undrained slope.

The stability of slopes in soils with nonlinear failure envelopes

1984 ◽  
Vol 21 (3) ◽  
pp. 397-406 ◽  
Author(s):  
J. A. Charles ◽  
M. M. Soares
Keyword(s):  
Slope Stability ◽  
Pore Pressure ◽  
Factor Of Safety ◽  
Pressure Ratio ◽  
Rapid Assessment ◽  
Failure Envelope ◽  
Stability Of Slopes ◽  
Simple Geometry ◽  
Failure Envelopes ◽  
The Stability

The failure envelopes of many soils are significantly nonlinear and the effect of this curvature on slope stability is examined. Charts, based on circular arc stability analyses, have been prepared and make possible the rapid assessment of the stability of slopes of simple geometry in uniform soils with curved failure envelopes. The effect on the factor of safety against stability failure of (i) the degree of curvature of the failure envelope of the soil, (ii) the magnitude of the pore pressure ratio within the slope, and (iii) the depth to a hard stratum has been investigated. Key words: depth factor, pore pressure, safety factor, shear strength, slope, stability.

A Comparative Study for Locating Critical Failure Surface in Slope Stability Analysis via Meta-Heuristic Approach

2018 ◽  
pp. 1-18 ◽  
Author(s):  
Jayraj Singh ◽  
A. K. Verma ◽  
Haider Banka
Keyword(s):  
Global Optimization ◽  
Stability Analysis ◽  
Slope Stability ◽  
Comparative Study ◽  
Factor Of Safety ◽  
Optimization Problem ◽  
Failure Surface ◽  
Slope Stability Analysis ◽  
Global Optimization Problem ◽  
Critical Failure Surface

Locating critical failure surface in a rock or soil slope is performed in stability analysis to access the optimal safe design of the slope. Finding the critical failure surface associated with a minimum factor of safety value in slope stability analysis is very cumbersome and becomes a global optimization problem in the field of geotechnical and mining engineering. The presence of many local minimal points in the search space and discontinuous function made this factor of safety margin big and proves to be a chief constraint global optimization problem. In this chapter, some meta-heuristic techniques such as genetic algorithm, particle swarm optimization algorithm are adopted for analyzing the critical failure surface. A comparative study has been done to analyze safety factor for the slope stability analysis. The outcome result acquires acceptable performance over existing methods and confirms the higher slope stability analysis. The validation and simulation design of the proposed methodology will be investigated by using “slide-tool” from rock science engineering.

A transient analysis of slope stability following drawdown after flooding of a highly plastic clay

1999 ◽  
Vol 36 (6) ◽  
pp. 1151-1171 ◽  
Author(s):  
G J Pauls ◽  
E Karl Sauer ◽  
E A Christiansen ◽  
R A Widger
Keyword(s):  
Stability Analysis ◽  
Pore Water ◽  
Factor Of Safety ◽  
Field Measurements ◽  
Stability Of Slopes ◽  
Pore Water Pressures ◽  
Seepage Model ◽  
Transient Seepage ◽  
The Stability ◽  
Plastic Clays

The stability of slopes at bridge abutments across the Carrot River in east-central Saskatchewan was not influenced significantly by drawdown after flooding in the spring of 1995. Traditional methods of analysis for rapid drawdown predicted the factor of safety of slopes on highly plastic clays of proglacial Lake Agassiz would drop to 0.65 from an initial value of 1.0. Deformation along a well-defined slip plane has persisted at a more or less constant, slow rate since the bridge was constructed in 1975. The river rose approximately 10 m during a flood in the spring of 1995, yet there was only minimal response in piezometers and no measurable increase in the rate of deformation recorded by inclinometers. Pore-water pressures from a steady state seepage model, which was calibrated from piezometer measurements, were integrated into a stability analysis. Changes in pore-water pressures caused by flooding and subsequent drawdown were characterized from a transient seepage model using the flood hydrograph as a flux boundary. The stability analysis integrated with the transient seepage model estimated the factor of safety would drop from 1.0 to 0.91 after drawdown. Field measurements indicated the reduction in factor of safety was even less.

Contrôle de la stabilité des remblais par la mesure des déplacements horizontaux

1974 ◽  
Vol 11 (1) ◽  
pp. 182-201 ◽  
Author(s):  
René Marche ◽  
Robert Chapuis
Keyword(s):  
Factor Of Safety ◽  
Soft Clay ◽  
Ground Surface ◽  
Soft Layer ◽  
The Stability ◽  
Horizontal Displacements

The horizontal displacements measured at the toe of eight embankments are analyzed as a function of the factor of safety. The embankments are built on layers of soft clay. Only the undrained stage is studied.When the factor of safety of the embankments is higher than about 1.4, the horizontal displacements on the ground surface, at the toe of the embankment seem to follow an elastic law which is highly dependent on the ratio of the thickness of the soft layer to the width of the embankment. When the factor of safety is lower than about 1.4, the horizontal displacements do not follow an elastic law, they increase considerably. Consequently, it is suggested that the horizontal displacements be precisely measured at the toe of embankments during construction. These measurements are simple and sensitive to the approach of failure, they can be efficiently used to control the stability of embankments. This study also gives some information concerning the variation of horizontal displacements versus depth.

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.

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