Numerical Analysis on Slope Stability Under Impact of Prolonged Antecedent Rainfall in Tropical Climates

Within a few decades, there have been quite a number of rainfall-induced landslide events occurring in many parts of Malaysia, especially in the urbanised hilly areas. The changes in hilly morphology because of weathering activities in humid tropical climates have increased the potential for rainfall-induced landslides, especially during prolonged antecedent rainfall. In addition to the bedrock geology influencing geohazards, the weathering profiles, slope gradient and rainfall pattern also can be responsible for landslides. A series of site investigation works were undertaken in the designated landslide-prone study site to obtain data on the characteristics, composition and mechanical response of the soil as well as the groundwater table located below the ground surface. The numerical transient seepage analysis by applying recorded average annual rainfall of approximately 2440 mm and limit equilibrium slope stability analysis was carried out and simulated on the landslide area using commercial software GeoStudio of SEEP/W and SLOPE/W respectively. The simulation outcomes establish the occurrence of a landslide may not necessarily be dependent on a significant rainfall event, yet, the extended period of antecedent rainfall may exert a predominant influence in initiating failure of the landslide-prone area.