Generalized Slice Method for Slope Stability Analysis

Abstract

ABSTRACT Many slice methods already proposed for slope stability analysis have two weak points, assumption on interslice forces and complicated calculation technique. In this paper, an extended wedge method in which equilibrium equations of forces acting on slices are directly presented and safety factors on interslice planes are defined, is proposed. Followings are clarified after mathematical consideration. If the problem to obtain safety factor along main slip surface is considered as optimization problem with constraints, the solution can be obtained even if the number of variables exceeds the number of equations. This means that the safety factor can be optimized not only by geometry of slip surface but also by assumption on interslice forces. The equilibrium equations of forces are sufficient to obtain and minimize safety factor without equilibrium equations of moment. Safety factor, Fsmin, which assumes no tangential force on interslice planes, and safety factor Fsmax, which assumes that interslice planes are just failing, are minimum and maximum limit of safety factors, respectively. Together with Fsmed which assumes that safety factor along main slip surface is equal to ones along interslice planes, Fsmin and Fsmax are the standard for evaluation of other slice methods from the state of forces acting on interslice planes. Then, some comparisons suggest that Fellenius method and simplified Janbu method give the lowest safety factors which are nealy equal to Fsmin and that Morgenstern-Price method gives the safety factor higher than Fsmed.