Uncertainty and reliability analysis applied to slope stability

Abstract

In this paper, reliability analysis of slope stability is presented using two methods of uncertainty first-order second-moment method (FOSM) and Monte Carlo simulation method (MCSM). The results of these methods are compared using four recognized methods of slope stability. These are Ordinary method of slices, simplified Bishop's method, simplified Janbu's method and Spencer's method. Two illustrative examples are presented in this paper: one is homogenous slope and the other is non-homogeneous layered slope. The study shows that the reliability index ( β) is independent of the seed random number generator and a sample size of 700 or greater is a good choice for MCSM. In the case of homogeneous slope a good agreement is observed between the calculated ( β) using FOSM and MCSM for both the Ordinary and the Bishop's method. However, slight difference in ( β) is observed between the two uncertainty methods whether Janbu's method or Spencer's method is used. In the case of the layered slope good agreement is obtained between the two uncertainty methods for Ordinary, Bishop and Janbu methods. Similar to example 1, Spencer's method shows also slight difference in ( β) between FOSM and MCSM methods. Model uncertainty is addressed by evaluating the relative performance of the three slope stability methods i.e. Ordinary, Bishop and Janbu methods as compared to Spencer's method.