Back analysis of slope failure induced by rainfall infiltration

Abstract

The slope stability issues concerning rainfall induced slope failures constitute a major threat to both lives and property worldwide particularly in the tropical climate of Malaysia which is characterized by very intense and long duration rainfall. The aim of this study is to investigate landslide occurrence due to rainfall infiltration through numerical simulation. The objectives are to determine the soil properties of the failed slope, to study the hydrological data of the slope and lastly to analyse the rainfall-induced slope failure by observing the factor of safety (FOS) at failure. The study focuses on the failure mechanisms of a landslide that occurred at Phase 8, Taman Sri Gombak, Batu Caves on 25th May 2011 by utilizing well established SEEP/W and SLOPE/W developed by Geoslope. The findings of the back analysis suggests that with the factor of safety 0.992, the slope begins to exhibit failure on 23rd May due to the increase level of ground water table that eliminates the apparent strength contributed by matric suction in the unsaturated soil system. All in all, it is proven that beside the contributing factors such as soil strength properties, soil mass and geometry, the factor of safety can be altered by the fluctuating pore water pressure induced by rainfall infiltration which in return greatly influences stability of slopes.