A Search for the Critical Slip Surface in Three-Dimensional Slope Stability Analysis

Abstract

The studies dealing with slope stability analyses within the framework of limit equilibrium can be classified into two major categories: the first is formulation of factors of safety i.e. the problem of how to calculate the factor of safety for a given slip surface, and the second refers to minimization of factors of safety i.e. the problem of how to determine the minimum factor of safety and the corresponding critical slip surface. From the latter aspect of the studies, an efficient and practical minimization approach for the 3-D slope stability analysis, based on Dynamic Programming (Baker, 1980) and Random Number Generation, is proposed in this paper. This approach can simultaneously provide the minimum factor of safety, and the corresponding critical slip surface for a general 3-D slope. The 3-D simplified Janbu method, which was developed by Ugai (1988) and Ugai and Hosobori (1988), is incorporated with the proposed approach. The slope stability analysis presented in this paper has two noticeable characteristics: 1) the potential slip surface is not restricted to any particular shape; 2) the approach is available for either inhomogeneous problems or cases in which no symmetrical plane appears. The developed analysis method was implemented into a computer program called 3D-DYRANUT. Using this program, several example problems, including a multilayered convex slope as well as an actual slope failure caused by an earthquake, were analyzed and the results are reported.