Back Analysis of Slope Failure Using Finite Element with Point Estimate Method (FEM-PEM)

Abstract

This paper investigates the slope failure in Precinct 9, Putrajaya, Malaysia by using numerical back analysis method. The catastrophic slope failure was triggered by a cumulative rainfall of 210 mm that occurred 2 days before the occurrence of slope failure. Site investigation that includes borehole sampling was immediately conducted to obtain representative information for the study area. The slope can be divided into 3 layers namely gravelly silt, silt and bedrock. Due to the uncertainty about the actual cause of failure initiation, back analyses have been performed via finite element shear strength reduction method for considering various probable mechanisms. In order to deal with the uncertainty and variability of the soil parameters, the Point Estimate Method (PEM) approach that assumed a normal and uncorrelated distribution was adopted in this study. Analysis results show that the slope failure is mainly influenced by the shear strength of the silt layer where the cohesion and friction angle at failure were 11 kPa and 20° respectively. Besides, the modeled circular slip surface also agrees well with the observed one.