Factor of Safety Variations of Residual Soil Slopes under Rainfall Loading

Climate change has resulted in the formation of rainfall behaviour that is aberrant from historical trends. Consequently, this leads to escalation of the dangers of slope failures due to rainfall. Factor of safety distribution map is a common tool used to record the possibility of slope failure, by indicating the fac-tor of safety (FoS) of slopes in an area. In this study, FoS distribution map was developed for Bukit Timah Granite formation in Singapore utilizing Transient Rainfall Infiltration and Grid-based Regional Slope-Stability Model (TRIGRS). Several slopes were analyzed to evaluate the accuracy of the FoS distribution map. The analyses were performed via 2-D numerical analyses involving seepage and slope stability analyses on the investigated slopes that have experienced slope failure in the past. The results of the analyses indicated that the FoS from the map were lower as compared to those from 2-D numerical analyses. Potential sources of the discrepancy could arise from the usage of infinite slope model as well as 1-D vertical infiltration in the TRIGRS software. To minimize the errors associ-ated with the 1-D infiltration and infinite slope model, correction factors were proposed in this study.