Search published articles


Showing 12 results for Slope Stability

Mahin Roosta R., Sadaghyani M.h., Pak A.,
Volume 3, Issue 3 (9-2005)
Abstract

Existence of discontinuities causes higher deformability and lower strength in rock masses. Thus joints can change the rock mass behaviour due to the applied loads. For this reason properties and orientation of the joint sets have a great effect on the stability of rock slopes. In this paper, after introducing some numerical methods for evaluating the factor of safety for the stability of slopes, stability of jointed rock slopes in the plane strain condition is investigated with the strength reduction technique this method is modified and applied in the multilaminate framework. First of all, stability of one homogeneous rock slope is investigated and compared with the limit equilibrium method. Then stability of a layered rock slope is analyzed with some modifications in the strength reduction technique. Effects of orientation, tensile strength and dilation of layered joint sets on the factor of safety and location of the sliding block are explained.
Habib Shahnazari, Hosein Salehzadeh, Amin Askarinejad,
Volume 6, Issue 1 (3-2008)
Abstract

Classical soil mechanics involves the study of fully saturated soils. However, many problems encountered in geotechnical engineering practice involve unsaturated soil, in which behavior is significantly different from classical saturated soil. Negative pore pressure and capillary forces develop a virtual cohesion between the grains of semi saturated soils. This kind of cohesion is dependent on different factors such as grain size, saturation degree, soil-water characteristic curve and relative density of the soil. In this research the virtual cohesion of fine silty sand with 5% water content and a saturation degree of 17% is estimated. A vertical slope is constructed and is accelerated in the geotechnical centrifuge until failure. During the test, the model was monitored by a wireless video camera, attached to the strong box. The cohesionless tested sand was unsaturated. Based on the scaling laws and considering parameters such as sample unit weight, failure acceleration and the sample dimensions, a slope stability analysis was performed, and the virtual cohesion generated in the sample was calculated. The factor of safety of the prototype modeled in the centrifuge is calculated either by Finite Element Method and Finite Difference Method by using the resulted virtual cohesion from physical modeling. Results of this research show the validity of physical modeling for calculating the virtual cohesion in unsaturated silty sand.
Faradjollah Askari, Orang Farzaneh,
Volume 6, Issue 1 (3-2008)
Abstract

Although some 3D slope stability algorithms have been proposed in recent three decades, still role of pore pressures in three dimensional slope stability analyses and considering the effects of pore water pressure in 3D slope stability studies needs to be investigated. In this paper, a limit analysis formulation for investigation of role of the pore water pressure in three dimensional slope stability problems is presented. A rigid-block translational collapse mechanism is used, with energy dissipation taking place along planar velocity discontinuities. Results are compared with those obtained by others. It was found that water pressure causes the three-dimensional effects to be more significant, especially in gentle slopes. This may be related to the larger volume of the failure mass in gentle slopes resulting in more end effects. Dimensionless stability factors for three dimensional slope stability analyses are presented - including the 3D effect of the pore water pressure – for different values of the slope angle in cohesive and noncohesive soils.
M. Miraboutalebi, F. Askari, O. Farzaneh,
Volume 9, Issue 4 (12-2011)
Abstract

In this paper, the effect of bedrock inclination on seismic performance of slopes is investigated. The study was conducted based

on dynamic analysis of different slopes, evaluation of the earthquake acceleration in sliding mass, and calculating the

permanent displacement of the slope, using Newmark sliding block. The investigation indicates that variation of the bedrock

inclination may cause the acceleration magnitude and the displacement in the sliding mass to reach to their maximum level.

This may happen in conditions that the mean period of the acceleration time history on failure surface (Tmt) and the

predominant period of the slope (Ts ) are close to each other. Typical results are presented and discussed. A two dimensional

model of a typical slope was considered and conducting dynamic analyses, the slope performance was studied for different

geometries, strength parameters and shear wave velocities. Such a performance has been studied by assessing the record of

acceleration in sliding mass (the mass above the critical sliding surface) and calculating the slope displacement using Newmark

method. It is shown that neglecting the effect of bedrock inclination, would lead to non-real results in assessing the seismic slope

performance.


F. Askari, A. Totonchi, O. Farzaneh,
Volume 10, Issue 2 (6-2012)
Abstract

Presented is a method of three-dimensional stability analysis of convex slopes in plan view based on the Lower-bound theorem of
the limit analysis approach. The method’s aim is to determine the factor of safety of such slopes using numerical linear finite
element and lower bound limit analysis method to produce some stability charts for three dimensional (3D) homogeneous convex
slopes. Although the conventional two and three dimension limit equilibrium method (LEM) is used more often in practice for
evaluating slope stability, the accuracy of the method is often questioned due to the underlying assumptions that it makes. The
rigorous limit analysis results in this paper together with results of other researchers were found to bracket the slope stability
number to within ±10% or better and therefore can be used to benchmark for solutions from other methods. It was found that using
a two dimensional (2D) analysis to analyze a 3D problem will leads to a significant difference in the factors of safety depending
on the slope geometries. Numerical 3D results of proposed algorithm are presented in the form of some dimensionless graphs which
can be a convenient tool to be used by practicing engineers to estimate the initial stability for excavated or man-made slopes


F. Askari, M. R. Arvin, O. Farzaneh,
Volume 11, Issue 2 (11-2013)
Abstract

Seismic stability of slopes is typically evaluated by conventional methods under the assumption that the slope is subjected to an

earthquake just for one time. In general, time histories of loadings on slopes are unknown and loads are of variable repeated

nature. Shakedown phenomenon can be considered as a safe state for slopes subjected to variable repeated loadings. In this study,

lower bound dynamic shakedown theorem is employed for the seismic stability of slopes as a comprehensive verification. A

numerical method applied previously to evaluate roads under the traffic loads was modified to make it appropriate for dynamic

shakedown analysis in the present study. The numerical method is based on the combination of finite element and linear

programming methods. Critical PGA is employed as a comparative parameter to compare shakedown and pseudostatic methods.

Results show that, unlike pseudostaic method, shakedown approach is able to consider dynamic properties of load and slope.

Also, it is indicated that contrary to pseudostaic approach, shakedown solutions are different for slopes and embankments.

Shakedown and pseudostaic critical PGA versus dynamic properties of load and slope creates four distinct zones. It is shown that

the forgoing zones can be used as appropriate tools for seismic zonation of slopes based on their short term and long term safety


J. Nazari Afshar, M. Ghazavi,
Volume 12, Issue 1 (1-2014)
Abstract

The Stone-column is a useful method for increasing the bearing capacity and reducing settlement of foundation soil. The prediction of accurate ultimate bearing capacity of stone columns is very important in soil improvement techniques. Bulging failure mechanism usually controls the failure mechanism. In this paper, an imaginary retaining wall is used such that it stretches vertically from the stone column edge. A simple analytical method is introduced for estimation of the ultimate bearing capacity of the stone column using Coulomb lateral earth pressure theory. Presented method needs conventional Mohr-coloumb shear strength parameters of the stone column material and the native soil for estimation the ultimate bearing capacity of stone column. The validity of the developed method has been verified using finite element method and test data. Parametric studies have been carried out and effects of contributing parameters such as stone column diameter, column spacing, and the internal friction angle of the stone column material on the ultimate bearing capacity have been investigated.
C. Vieira,
Volume 12, Issue 1 (1-2014)
Abstract

This paper presents a simplified approach to estimate the resultant force, which should be provided by a retention system, for the equilibrium of unstable slopes. The results were obtained with a developed algorithm, based on limit equilibrium analyses, that assumes a two-part wedge failure mechanism. Design charts to obtain equivalent earth pressure coefficients are presented. Based on the results achieved with the developed computer code, an approximate equation to estimate the equivalent earth pressure coefficients is proposed. Given the slope angle, the backslope, the design friction angle, the height of the slope and the unit weight of the backfill, one can determine the resultant force for slope equilibrium. This simplified approach intends to provide an extension of the Coulomb earth pressure theory to the stability analyses of steep slopes and to broaden the available design charts for steep reinforced slopes with non-horizontal backslopes
Khaled Farah, Mounir Ltifi, Tarek Abichou, Hedi Hassis,
Volume 12, Issue 3 (7-2014)
Abstract

The purpose of this study is to compare the results of different probabilistic methods such as the perturbation method, Stochastic Finite Element Method (SFEM) and Monte Carlo Method. These methods were used to study the convergence of direct approach for slope stability analysis and are developed for a linear soil behavior. In this study, two dimensional random fields are used and both the First Order Reliability Method (FORM) and Limited Step Length Iteration Method (LSLIM) have been adopted to evaluate the reliability index. The study found that the perturbation method of the second order is easy to apply using the field’s theory because accuracy is reached even with different coefficients of variation of input variables, while the spectral finite element method yields accurate results only for high levels of solution development.
O. Farzaneh, F. Askari, J. Fatemi,
Volume 12, Issue 4 (12-2014)
Abstract

AWT IMAGEPresented is a method of two-dimensional analysis of the active earth pressure due to simultaneous effect of both soil weight and surcharge of strip foundation. The study’s aim is to provide a rigorous solution to the problem in the framework of upper-bound theorem of limit analysis method in order to produce some design charts for calculating the lateral active earth pressure of backfill when loaded by a strip foundation. A kinematically admissible collapse mechanism consisting of several rigid blocks with translational movement is considered in which energy dissipation takes place along planar velocity discontinuities. Comparing the lateral earth forces given by the present analysis with those of other researchers, it is shown that the results of present analysis are higher (better) than other researchers’ results. It was found that with the increase in AWT IMAGE, the proportion of the strip load (q) which is transmitted to the wall decreases. Moreover, Increasing the friction between soil and wall ( AWT IMAGE) will result in the increase of effective distance ( AWT IMAGE). Finally, these results are presented in the form of dimensionless design charts relating the mechanical characteristics of the soil, strip load conditions and active earth pressure.


Yones Sojodi,
Volume 14, Issue 4 (6-2016)
Abstract

The paper present the results of various experimental and numerical studies on slopes, small scale physical modeling of slope under surcharge load were performed in loose sand environment. Digital images were captured during the incremental loading from side of model simultaneously. The Particle Image Velocimetry (PIV) and 3D numerical model was applied to investigate the slope under surcharge loading and some of the other important factors that control the performance of piles are investigated. The factors of safety and location of critical failure surfaces of reinforced and unreinforced slopes obtained and compared for various slopes. For homogenous slope, it is found for stabilized slope with piles, the 3D failure surface shape in front of piles is triangle, unlike its conical shape in laterally loaded piles. The paper also studies numerically the effect of soft bound effect, soil properties, pile spacing, pile position and surcharge distance effects on stabilized and none stabilized slopes. The results indicate that the depth of soft soil layer from ground surface and its angles with horizontal direction has importance effect on optimum location of stabilized pile. Studies on pile space effects shows with increasing pile space, arching phenomenon didn’t developed and partial pressure of supported portion transferred to un supported soil portion and the potential failure volume of the slope becomes large.


Junxin Liu, Chunhe Yang, Jianjun Gan, Yutian Liu, Wei Liu, Qiang Xie,
Volume 15, Issue 6 (9-2017)
Abstract

Abstract: Rainfall is an important triggering factor influencing the stability of soil slope. Study on some influences of the rainfall on the instability characteristics of unsaturated soil embankment slope has been conducted in this paper. Firstly, based on the effective stress theory of unsaturated soil for single variable, fluid-solid coupling constitutive equations were established. Then, a segment of red clay embankment slope, along a railway from Dazhou to Chengdu, damaged by rainfall, was theoretical and numerical-simulating researched by considering both the runoff-underground seepage and the fluid-solid coupling. The failure characteristics of the embankment slope and the numerical simulation results were in excellent agreement. In the end, a sensitivity analysis of the key factors influencing the slope stability subjected to rainfall was performed with emphasis on damage depth as well as infiltration rainfall depth. From the analysis in this paper, it was concluded that the intensity of rainfall, rainfall duration and long-term strength of soil have most effect on slope stability when subjected to rainfall. These results suggest that the numerical simulation can be used for practical applications.



Page 1 from 1     

© 2019 All Rights Reserved | International Journal of Civil Engineering

Designed & Developed by : Yektaweb