Slope Reliability Analysis Using the First-Order Reliability Method

Abstract

This chapter pertains to a study on the reliability evaluation of earth slopes under a probabilistic framework. This study is concerned in the first phase with the determination of reliability index and the corresponding probability of failure associated with a given slip surface and then in the second phase with the determination of the critical probabilistic slip surface and the associated minimum reliability index and the corresponding probability of failure. The geomechanical parameters of the slope system have been treated as random variables for which different probability distributions have been assumed. The reliability analyses have been carried out using two methods, namely, the approximate yet simple mean-value first-order second-moment (MVFOSM) method and the rigorous first-order reliability method (FORM). Based on a benchmark illustrative example of a simple slope in homogeneous soil with uncertain strength parameters along a slip circle, an effort has been made to numerically demonstrate the nature and level of errors introduced by adopting the MVFOSM method for reliability analysis of earth slopes still widely used in the geotechnical engineering practice, vis-à-vis a more accurate method such as the FORM.