EFFECTS OF UNCERTAINTY IN THE HYDRAULIC PROPERTIES FOR THE SEEPAGE ANALYSES OF RAINWATER INFILTRATION

Rainwater infiltration is the crucial factor in any evaluation of rainfall-induced slope stability. The amount of rainwater infiltration is dependent on factors such as the rainfall intensity, the rainfall duration, the slope geometry, the hydraulic properties of the soil, and the initial pore-water pressure distribution. In this paper the effects of the variability in hydraulic properties of unsaturated soil on the rainwater's infiltration are investigated and discussed. Different hydraulic conductivity functions (HCFs) by considering the uncertainty in saturated volumetric water content (theta(s)) and the soil-water characteristic curve (SWCC) are proposed. The seepage analyses for five cases (incorporating the uncertainty in theta(s), SWCC, and hydraulic conductivity, k(s)) are conducted in this study. The results indicated that the effect of the variability in hydraulic properties of the unsaturated soil on the infiltration is much dependent on the initial suction in the slope soil. If the initial suction level is low (relatively wet conditions), then the variability in the hydraulic properties has an insignificant effect on the infiltration. On the contrary, if the initial suction level is high (relatively dry conditions), then the variability in the hydraulic properties has a significant effect on the infiltration.