Study on Failure Mechanism of Instability About Unsaturated Soil Slope Under Extreme Rainfall

Landslide is a major natural disaster, and large number of landslide disasters show that rainfall infiltration is a main factor to induce instability for unsaturated soil slope. To explore the failure mechanism of soil slope under extreme rainfall, the influence of rainfall infiltration for soil slope’s saturation, pore water pressure and displacement are analyzed based on fluid-structure coupling and theory of unsaturated soil mechanics under different extreme rainfall conditions. The results show that: (1) It has same rainfall discharge and rainfall duration for the four kinds of rainfall patterns, but they have different space-time effect on soil slope’s saturation, pore water pressure and displacement. (2) The rainfall pattern has large impact on slope’s displacement, and gradually increasing rainfall has most effective for slope’s displacement than other rainfall patterns after rainfall last 48 h, followed by first increasing and then decreasing rainfall after the first type, the third is gradually decreasing rainfall, and the least is stability rainfall. (3) Different rainfall patterns have different danger points during rainfall, but it occurs at the time that when rainfall intensity up to the maximum. According to the paper, gradually decreasing rainfall has most impact on slope’s stability at early-term of rainfall, first increasing and then decreasing rainfall has most impact on slope’s stability at medium-term of rainfall, and gradually increasing rainfall has most impact at last-term of rainfall.