Effect of antecedent rainfall patterns on rainfall‐induced slope failure.

Abstract

Rainfall‐induced slope failure occurs in many parts of the world especially in the tropics. Many rainfall‐induced slope failures have been attributed to antecedent rainfalls. Although, it has been identified as a cause of rainfall‐induced slope failure, the pattern or distribution of the antecedent rainfall has not received adequate attention. In this study, parametric studies were performed using three typical rainfall patterns identified by analysis of available rainfall data of Singapore and two different soil types to represent high and low conductivity residual soils of Singapore. Antecedent rainfall patterns were applied on soil slopes and a transient seepage analysis was conducted. The computed pore‐water pressures were used in stability analyses to calculate factor of safety of the slope. Results indicated that antecedent rainfall affected stability of both high conductivity (HC) and low conductivity (LC) soil slopes. However, it affected the stability of LC soil slope more significantly than HC soil slope. Patterns of antecedent rainfall controlled the rate of decrease in factor of safety, the time corresponding to Fs(min) and the value of Fs(min). Delayed rainfall pattern resulted in the lowest minimum factor of safety, Fs(min), for HC soil slope and advanced rainfall pattern resulted in the lowest Fs(min) for LC soil slope.