scholarly journals Formation of Clay-Rich Layers at The Slip Surface of Slope Instabilities: The Role of Groundwater

Water ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2639
Author(s):  
Julia Castro ◽  
Maria P. Asta ◽  
Jorge P. Galve ◽  
José Miguel Azañón
Keyword(s):  
Clay Minerals ◽  
Slip Surface ◽  
Thick Layer ◽  
Friction Angle ◽  
High Plasticity ◽  
Slide Mass ◽  
Triggering Factor ◽  
Slope Instabilities ◽  
The Stability ◽  
Clay Layers

Some landslides around the world that have low-angle failure planes show exceptionally poor mechanical properties. In some cases, an extraordinarily pure clay layer has been detected on the rupture surface. In this work, a complex landslide, the so-called Diezma landslide, is investigated in a low- to moderate-relief region of Southeast Spain. In this landslide, movement was concentrated on several surfaces that developed on a centimeter-thick layer of smectite (montmorillonite-beidellite) clay-rich level. Since these clayey levels have a very low permeability, high plasticity, and low friction angle, they control the stability of the entire slide mass. Specifically, the triggering factor of this landslide seems to be linked to the infiltration of water from a karstic aquifer located in the head area. The circulation of water through old failure planes could have promoted the active hydrolysis of marly soils to produce new smectite clay minerals. Here, by using geophysical, mineralogical, and geochemical modelling methods, we reveal that the formation and dissolution of carbonates, sulfates, and clay minerals in the Diezma landslide could explain the elevated concentrations of highly plastic secondary clays in its slip surface. This study may help in the understanding of landslides that show secondary clay layers coinciding to their low-angle failure planes.

Movement and stability analysis of the Beaver Creek landslide, Saskatchewan, Canada

1985 ◽  
Vol 22 (3) ◽  
pp. 277-285 ◽  
Author(s):  
R. T. Yoshida ◽  
J. Krahn
Keyword(s):  
Stability Analysis ◽  
Key Words ◽  
Residual Strength ◽  
Case History ◽  
Single Unit ◽  
Slip Surface ◽  
Friction Angle ◽  
Slide Mass ◽  
History Of ◽  
Residual Values

This paper presents a case history of a multiblock landslide where the blocks move at varying rates along a common horizontal slip surface which follows the contact between stratified drift and underlying till. Movement measurements indicate that the blocks towards the toe move at a higher rate than blocks towards the scarp. Stability analyses show that the entire slide mass can be analyzed as a single unit as opposed to considering each block separately. This finding is compared with the analysis of other multiblock slides. The friction angle mobilized along the horizontal slip surface falls within the range of residual values measured in the laboratory. Key words: landslides, stability, analysis, translational slides, residual strength.

scholarly journals Stability of Reinforced Retaining Wall under Seismic Loads

2019 ◽  
Vol 9 (11) ◽  
pp. 2175 ◽  
Author(s):  
Liang Jia ◽  
Shikai He ◽  
Na Li ◽  
Wei Wang ◽  
Kai Yao
Keyword(s):  
Slip Surface ◽  
Retaining Wall ◽  
Tensile Force ◽  
Friction Angle ◽  
Unit Weight ◽  
Seismic Load ◽  
Seismic Loads ◽  
The Stability ◽  
Slice Method ◽  
Reinforced Retaining Wall

Based on the horizontal slice method (HSM) and assuming a log spiral slip surface, a method to analyze the stability of a reinforced retaining wall under seismic loads was established in this study by calculating the tensile force of the reinforcement. A parametric study was conducted on the normalized tensile force of the reinforcement, and it was observed that the normalized tensile force tends to increase with acceleration of the seismic load and the height of the backfill. Moreover, it also increases with soil unit weight, while it decreases with increased friction angle of the backfill soil, and the influence of soil cohesion on the normalized tensile force is not significant. The HSM method is proved to be suitable for analyzing the tensile force of reinforcement in retaining walls under seismic loads.

Influence of Anisotropic Internal Friction Angle on the Stability of Uniform Soil Slopes

2012 ◽  
Vol 170-173 ◽  
pp. 270-273 ◽  
Author(s):  
Lian Wei Zhang
Keyword(s):  
Slip Surface ◽  
Friction Angle ◽  
Soil Slope ◽  
Critical Slip Surface ◽  
Obvious Effect ◽  
Anisotropic Friction ◽  
Change Of Direction ◽  
Soil Slopes ◽  
Anisotropic Soil ◽  
The Stability

The effect of anisotropy of friction angle in natural deposited soil on the stability of soil slopes was studied in this paper. Stability analysis was performed on a uniform soil slope with anisotropic friction angle. Spencer’s method was used, and the variation of friction angle was assumed to be linear to the change of direction of the slip surface. It was shown that 7-10 percent of change in safety factor might achieve within a 10m-highed anisotropic soil slope. It was also found from the analysis that that frictional anisotropy had no obvious effect on the location of critical slip surface.

scholarly journals Examining the Effects of Suction and Nonlinear Strength Envelopes on the Stability of a High Plasticity Clay Slope

Geosciences ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 449
Author(s):  
Mengwei Xuan ◽  
Jack Montgomery ◽  
J. Brian Anderson
Keyword(s):  
Limit Equilibrium ◽  
Friction Angle ◽  
Stability Factor ◽  
High Plasticity ◽  
Slope Failures ◽  
Clay Deposits ◽  
Ring Shear ◽  
High Plasticity Clay ◽  
The Stability ◽  
Cut Slopes

Slope failures in high plasticity clay deposits are common occurrences in many parts of the world. In western and central Alabama, expansive Prairie clays are commonly found, and shallow slope failures have occurred in both fill and cut slopes containing these high plasticity clays. The objective of this study was to examine the effects of suction and the use of nonlinear strength envelopes on the embankment stability of a section of highway AL-5. The testing program consisted of fifteen ring shear tests performed using a Bromhead Ring Shear Device. The results of the tests were used to develop both linear and nonlinear fully softened and residual strength envelopes. The saturated strength envelopes are then used in a limit equilibrium slope stability analysis with and without the effects of suction. The results show stability (factor of safety >1) for all cases except the residual friction angle without suction. Given these results, large slope failures are unlikely to occur in this area, but surficial failures and deformations due to creep may be possible. These results demonstrate the importance of considering the effects of suction and nonlinear strength envelopes when examining the potential for shallow slope failures in high plasticity clays.

scholarly journals A limit equilibrium analysis of progressive failure in the stability of slopes

1978 ◽  
Vol 15 (1) ◽  
pp. 113-122 ◽  
Author(s):  
K. Tim Law ◽  
Peter Lumb
Keyword(s):  
Slip Surface ◽  
Progressive Failure ◽  
Limit Equilibrium ◽  
Friction Angle ◽  
Soil Mass ◽  
Local Failure ◽  
Equilibrium Analysis ◽  
Stability Of Slopes ◽  
The Stability ◽  
Definition Of

A limit equilibrium method of analysis is proposed for the study of progressive failure in slope stability under a long-term condition. Based on effective stresses, the formulation of the method is derived from consideration of force and moment equilibrium within the soil mass above a prospective slip surface. By dividing the soil mass into a number of vertical slices, recognition of local failure can be made. Once local failure takes place, post-peak strength is assumed to be operative. This then initiates a redistribution of interslice forces and leads to some further local failure. Thus realistic available strengths along the slip surface can be evaluated. This permits the definition of a final safety factor, which is expressed in terms of the actual available reserve of strength. The proposed method has been applied to three well documented case records and encouraging results have been obtained. Based on the assumption that post-peak strengths are given by a friction angle equal to the peak value and a zero cohesion, stability charts have been prepared for design purposes.

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).

scholarly journals Tunnel Back Analysis Based on Differential Evolution Using Stress and Displacement

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Joon-Sang An ◽  
Kyung-Nam Kang ◽  
Ju-Young Choi ◽  
Won-Suh Sung ◽  
Vathna Suy ◽  
...  
Keyword(s):  
Differential Evolution ◽  
Differential Evolution Algorithm ◽  
Back Analysis ◽  
Friction Angle ◽  
Internal Displacement ◽  
Average Error ◽  
Analysis Algorithm ◽  
Evolution Algorithm ◽  
Displacement Based ◽  
The Stability

The stability of tunnels has mainly been evaluated based on displacement. Because displacement due to the excavation process is significant, back analysis of the structure and ground can be performed easily. Recently, the length of a segment-lined tunnel driven by the mechanized tunneling method is increasing. Because the internal displacement of a segment-lined tunnel is trivial, it is difficult to analyze the stability of segment-lined tunnels using the conventional method. This paper proposes a back analysis method using stress and displacement information for a segment-lined tunnel. A differential evolution algorithm was adopted for tunnel back analysis. Back analysis based on the differential evolution algorithm using stress and displacement was established and performed using the finite difference code, FLAC3D, and built-in FISH language. Detailed flowcharts of back analysis based on DEA using both monitored displacement stresses were also suggested. As a preliminary study, the target variables of the back analysis adopted in this study were the elastic modulus, cohesion, and friction angle of the ground. The back analysis based on the monitored displacement is useful when the displacement is significant due to excavation. However, the conventional displacement-based back analysis is unsuitable for a segment-lined tunnel after construction because of its trivial internal displacement since the average error is greater than 32% and the evolutionary calculation is finalized due to the maximum iteration criteria. The average error obtained from the proposed back analysis algorithm using both stress and displacement ranged within approximately 6–8%. This also confirms that the proposed back analysis algorithm is suitable for a segment-lined tunnel.

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.

scholarly journals Stabilization of Algerian Clayey Soils with Natural Pozzolana and Lime

2017 ◽  
Author(s):  
Khelifa Harichane ◽  
Mohamed Ghrici ◽  
Said Kenai
Keyword(s):  
Shear Strength ◽  
Internal Friction ◽  
Friction Angle ◽  
Internal Friction Angle ◽  
Plasticity Index ◽  
Engineering Properties ◽  
High Plasticity ◽  
Expansive Clay ◽  
Clayey Soils ◽  
Natural Pozzolana

Cohesive soils with a high plasticity index present difficulties in construction operations because they usually contain expansive clay minerals. However, the engineering properties of soils can be improved by different techniques. The aim of this paper is to study the effect of using lime, natural pozzolana or a combination of both lime and natural pozzolana on plasticity, compaction and shear strength of two clayey soils classified as CH and CL according to the unified soil classification system (USCS). The obtained results indicated that for CH class clay soil, the plasticity index decreased significantly for samples stabilized with lime. On the other hand, for the soil classified as CL class clay, a high decrease in the plasticity index value was observed for samples stabilized with natural pozzolana compared to those stabilized with lime. Also, both the cohesion and internal friction angle in lime added samples were demonstrated to increase with time. The combination of lime and natural pozzolana exhibits a significant effect on the enhancement of both the cohesion and  internal friction angle at later stages. The lime-natural pozzolana combination appears to produce higher shear strength parameters than lime or natural pozzolana used alone.

scholarly journals Water Softening Mechanism and Strength Model for Saturated Carbonaceous Mudstone in Panzhihua Airport, China

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Ziwen Wang ◽  
Jifang Du ◽  
Shuaifeng Wu ◽  
Yingqi Wei ◽  
Jianzhang Xiao ◽  
...  
Keyword(s):  
Shear Strength ◽  
Water Saturation ◽  
Structural Characteristics ◽  
Water Immersion ◽  
Analytical Techniques ◽  
Friction Angle ◽  
Mechanical Tests ◽  
Water Softening ◽  
Softening Mechanism ◽  
The Stability

To identify the water softening mechanisms that caused landslides in Panzhihua Airport, China, property and saturation tests of the mudstones extracted from a representative landslide were proposed. In this paper, water saturation tests were carried out on samples of carbonaceous mudstone collected from the east side of the No. 12 landslide at the airport. A number of different analytical techniques and mechanical tests were used to determine changes in chemical composition, mineral assemblages, and mudstone structural characteristics, including shear strength, after the mudstone had been softened. Three kinds of changes caused by water and three mudstone softening stages are proposed. The results show that the water has a significant influence on the properties of the mudstone, so the stability of the mudstone in the watery period is a big threat to the upper structure. A model for water immersion mudstone strength softening is developed. The model incorporates a permeability coefficient, the hydraulic gradient, and time; the model can be used to determine the mudstone’s shear strength and internal friction angle. This study provides a reference for the study of rock softened by water immersion.

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