A Comparative Study on Reliability Analysis of Cohesive Soil Slope using Subset Simulation and Other Methods

Abstract

In geotechnical engineering, uncertainties arise due to variation in loads, soil characteristics, ground stratification and so on. Reliability analysis based on probabilistic approaches is particularly suitable to deal with such uncertainties. In this paper, a newly developed reliability analysis method, namely Subset simulation (SS) method has been implemented to study the stability of a cohesive slope. The results of reliability analysis obtained from SS method are also compared with three other methods, namely First order second moment method (FOSM), First order reliability method (FORM) and Direct Monte-Carlo simulation (MCS) method. The various reliability models have been used in a spreadsheet environment using MS-Excel. The developed spreadsheet-based platform implementing all four methods contains two common models i.e. deterministic model and the uncertainty model. The SS method uses another model called uncertainty propagation using subset simulation (UPSS) in addition to the two above-mentioned models. The factor of safety  of the slope is determined using ordinary method of slices under undrained condition. The probability of failure (  and its corresponding reliability index  of the proposed slope has been determined using all four methods. A software called Geo-Studio (SLOPE/W) has been used to tally the results of reliability analysis of the slope considered herein. The results obtained from the different methods show that the SS method gives better performance in terms of efficiency and resolution especially at low failure probability i.e., . Also, the SS method helps in identifying the significant depth where the most probable critical slip surface is located.