Estimation of Change in Slope Stability Due to Rainfall Varied with Time, Based on Unsaturated Soil Mechanics

Recently, slope failure due to rainfall occurs frequently and inflicts serious damage. However, slope characteristics that reflect stability, such as gradient, length, thickness of weathered layer, and groundwater condition, differ from one slope to another. Because of this, it is difficult to estimate the risk of slope failure using a single uniform standard. A simple way to model a slope and estimate risk according to rainfall pattern is needed. In this study, a way to estimate slope stability in the framework of unsaturated soil mechanics is proposed. Here, the surface failure of a long slope covered with weathered soil is the target. Various slope gradients and rainfall intensities are considered as influential factors on slope stability. First, rainfall infiltration is simulated with soil/water/air coupled finite element analysis code, DACSARMP. Next, the factor of safety is calculated using the distributions of pore-water pressure and soil moisture obtained from seepage analysis.