Slope Stability Characteristic of Unsaturated Weathered Granite Soil in Korea considering Antecedent Rainfall

Abstract

In this paper, effects of antecedent rainfall on stability of the unsaturated weathered granite slope at Inje, Korea were investigated. Effect of antecedent rainfall was considered in the numerical analysis using initial condition of matric suction, which was induced from field measurement. We also investigated case histories of slope failure, rainfall data, geotechnical properties, soil-water characteristic curve (SWCC) and hydraulic conductivity in those areas. Several sets of numerical stability analysis were performed on unsaturated slope with different initial matric suction. Result of the analyses indicated that the higher initial matric suction (less antecedent rainfall) of the unsaturated weathered granite slope delayed the slope failure. Also, unsaturated slope with higher saturated permeability is more vulnerable to rainfallinduced landslide than that with lower saturated permeability due to rainfall infiltration. Numerical analysis also indicated that a slope with wetting SWCC reached the failure condition earlier than a slope with drying SWCC.