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Totonchi A.,Islamic Azad University at Tehran | Askari F.,Iran International Earthquake Engineering Institute | Farzaneh O.,University of Tehran
Iranian Journal of Science and Technology - Transactions of Civil Engineering | Year: 2012

It is well known that the plan curvature of curved slopes has an influence on the stability of the slopes. This paper aims to present a method of three-dimensional stability analysis of concave 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 concave 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 were found to be closely conservative results to exact solutions 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 lead to a significant difference in the factors of safety depending on the slope geometries. Numerical 3D results of the proposed algorithm are presented in the form of some dimensionless graphs, which can be a convenient tool for use by practicing engineers to estimate the initial stability for excavated or man-made slopes. The results obtained using this 3D method show that the stability of concave slopes in plan view increases as the relative curvature R/H and the relative width of slope decrease. © Shiraz University.


Totonchi A.,Islamic Azad University at Marvdasht | Askari F.,Iran International Earthquake Engineering Institute | Farzaneh O.,University of Tehran
Iranian Journal of Science and Technology - Transactions of Civil Engineering | Year: 2012

In this paper, application of stress fields in computation of seismic active lateral forces on retaining walls is considered using the lower bound method of limit analysis. Finding the exact solution of boundary value problems in engineering fields is a complicated problem in most applied cases and from this point of view, use of the limit state methods is very beneficial for engineers. In limit analysis method, in spite of exact solution of the problem, the upper and lower bound of the limit load are determined. The lower bound of the exact solution can be obtained by use of different admissible stress fields in different regions of the media divided by stress discontinuity surfaces. Earthquakes have unfavorable effects of increasing active and decreasing passive lateral earth pressure, so to investigate how the lateral earth pressure is affected, extensive numerical results based on the limit analysis method reported by Chang and Chen. This paper is devoted to finding an Analytical solution to investigate the lateral force affection on retaining walls, using mathematical relations based on lower bound limit analysis method. This process include the calculation of direction and magnitude of active lateral earth pressure. Numerical results of the proposed algorithm are presented in some practical dimensionless graphs. © Shiraz University.


Askari F.,Iran International Earthquake Engineering Institute | Totonchi A.,Islamic Azad University at Marvdasht | Farzaneh O.,University of Tehran
International Journal of Civil Engineering | Year: 2012

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.


Askari F.,Iran International Earthquake Engineering Institute | Totonchi A.,Islamic Azad University at Marvdasht | Farzaneh O.,University of Tehran
Scientia Iranica | Year: 2012

In this paper, the lower-bound techniques of limit analysis are applied to obtain lateral earth pressures of rigid retaining walls subjected to earthquake forces. The well-known MononobeOkabe analysis is a direct modification of the coulomb wedge analysis. In this analysis, the earthquake effects are replaced by a quasi-static inertia force whose magnitude is computed on the basis of the seismic coefficient concept. This paper is describing an analytical solution to investigate the lateral force affect on retaining walls, using mathematical relations based on a lower bound limit analysis method. The lower bound of the exact solution can be obtained by use of different admissible stress fields in different regions of the media divided by stress discontinuity surfaces. This process is included in calculation of the direction and magnitude of passive lateral earth pressure. Numerical results of the proposed algorithm are presented in some practical dimensionless graphs. © 2012 Sharif University of Technology. Production and hosting by Elsevier B.V. All rights reserved.

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