Extreme rainfall analysis for slope stability evaluation

Abstract

Slopes in tropical region are prone to frequent rainfall-induced failures; hence the evaluation of slope stability has to consider the rainfall characteristics and other factors related to rainfall infiltration. This paper demonstrates the results of numerical simulation using Seep/W for the evaluation of rainfall-induced slope instability at five selected sites at Johor Bahru, Malaysia The slopes were assigned with 1-day, 2-day, 3-day, 5-day, 7-day, 14-day and 30-day extreme rainfall of ten-year return period. A suction envelope was obtained for each site and slope stability analysis was performed for the corresponding suction envelope. The results show that the reduction in factor of safety is relatively more significant for fine-grained soil. The finding was verified by field observation after the slopes were subjected to a series of intense rainfalls in December 2006. The application of extreme rainfall in slope stability analysis gives a good prediction of rainfall-induced slope failure.