Slope stability against rainfall and preventive measures

Abstract

Slope failures caused by rainfall are common occurrences in Singapore and

Southeast Asia. Many residual soil slopes have a deep groundwater table with a

thick unsaturated soil zone above the water table. Infiltration rate into slopes is

governed by permeability of the unsaturated soil above the groundwater table. As

a result, changes in negative pore-water pressure or soil suction and

consequently in shear strength of unsaturated soil are a function of water content.

NTU and HDB have embarked on research collaboration to study the mechanism

of rainfall infiltration into residual soil slopes in Singapore under local climatic

conditions and the effects of rainfalls on stability of slopes. Unsaturated soil

mechanics and unsaturated soil properties are used in assessing stability of

slopes against rainfall. Measurements of soil properties are carried out using

unsaturated soil apparatuses and technology. In addition, preventive measures for

rainfall-induced slope failures are investigated using the principles of unsaturated

soil mechanics. Preliminary results of the assessment and preventive measures

based on unsaturated soil mechanics principles are illustrated.