MODELLING OF SLOPE FAILURE USING A GLOBAL OPTIMIZATION TECHNIQUE

Abstract

This paper deals with modelling of slope failure of natural slopes using the RST-2 algorithm, a random search global optimization technique. The factor of safety equation for a given slope based on Janbu's method of slices has been used in the analysis, using the co-ordinates of the slip surface. By the RST-2 algorithm the critical non-circular slip surface is located by determining the unique combination of the co-ordinates of the slip surface which minimize the factor of safety. Although any optimization technique could be used for the analysis, the RST-2 algorithm has been particularly selected since (1) it attempts to determine the global rather than the local optimal solution;(2) it does not require any continuity and differentiability conditions of the functions appearing in the optimization problem (in this case the objective function is a discontinuous function); (3) it does not require any initial guess value of the slip surface to initiate the algorithm, but requires an approximate lower and upper bound of the co-ordinates of the slip domain; (4) it is easy to programme, and can be applicable to a wide variety of problems. The model developed has been successfully applied to three original case studies. A comparison of the results between Bishop's method (circular), and Janbu's method (non-circular) using the hit and trial approach for the location of the critical slip surface and the RST-2 algorithm as a numerical technique for global optimization has been made. It can be concluded that the RST-2 algorithm is a very efficient, accurate and convenient algorithm to use for determining the critical failure surface and its corresponding minimum factor of safety. Moreover, the failure surface is not assumed but is arrived at by only providing the domain of the failure surface as the input