Rainfall characteristics for anisotropic conductivity of unsaturated soil slopes

The purpose of this study was to investigate the effects of the anisotropic ratio on the stability of slopes using the reliability index approach. A numerical analysis of the relationship between the three rainfall patterns, advanced, normal and delayed, and the anisotropic ratios was designed. This study also considered three different soil properties (sand, silt, and clay) to simulate rain infiltration. In this study, probability analysis was used to evaluate the stability of unsaturated soil slopes. The finite element computer program Geo-Studio was used to simulate the process of rainwater infiltrating a slope. The pore-water pressure results evaluated from seepage analysis (SEEP/W) were imported into the slope stability program (SLOPE/W). Results for the anisotropic ratio of hydraulic conductivity indicate that when the anisotropic ratios become higher, the reduction in the reliability index is insignificant. In addition, the simulation results indicated that when saturated hydraulic conductivity (k (s)) was less than rainfall intensities (I), the percentage probability of the occurrence of a landslide was larger than when k (s) was greater than I. Finally, in the cases of anisotropic k (s), stability of the high ratio soil slopes was not found to be sensitive to the reliability index variation during the simulation period. Moreover, when k (s) was greater than I, slope stability decreased earlier than was the case in the opposite situation.