Slope susceptibility map for preventive measures against rainfall-induced slope failure

Abstract Rainfall-induced slope failures frequently occurs in many urban areas around the world especially due to the impact of the global warming. Some slope failures result in casualties that have negative impacts on urban sustainability. The slope failures are normally observed near slope surface within the unsaturated zone above the groundwater table. Hence, it is important to incorporate the unsaturated soil mechanics principles in analysing the slope stability during rainfall. This study focuses predominantly on the regional stability analyses of residual soils within the Jurong Formation and Bukit Timah Granite in Singapore. The objective of the study is to develop slope susceptibility map as part of preventive measures against extreme rainfall conditions. The slope susceptibility map was evaluated using 2-D numerical analyses of slopes with historical failure. The recently developed sustainable retaining structure system, GeoBarrier System (GBS) is investigated to understand its suitability as a preventive measure for critical slopes with high risk as identified from the slope susceptibility map. Using Transient Rainfall Infiltration (TRIGRS) and Grid-Based Regional Slope Stability Analysis (Scoops3D), the pore-water pressure distributions and factors of safety (FS) within each zone are determined. The results from slope susceptibility maps and 2-D numerical analyses are consistent. Moreover, the incorporation of GeoBarrier System on the critical slope is demonstrated to be an effective slope stabilization measure based on the numerical simulations of two-dimensional analyses.