Unsaturated Seepage Characteristics of Slope under Rainfall Infiltration

In order to analyze unsaturated seepage characteristics of slope under rainfall infiltration, a rainfall simulation system and real-time monitoring system were employed for conducting model tests to simulate the rainfall-induced unsaturated soil slope failure process in this study. The real-time response of infiltration rate and wetting front of soil slope with different slope angles, different compaction degrees and different locations under different rainfall conditions were recorded and analyzed. Results show that steep slope and high compaction degree soil are not conducive to rainfall infiltration, while gentle slope and low compaction degree soil have a quick change of infiltration rate; the concept of test wetting front is proposed due to the real-time law of actual soil suction and water content under rainfall conditions are not synchronized, and the water content (suction) wetting front point can be determined by a linear intersection of water content (suction) real-time curve transition zone and residual water content (suction) after rainfall; considering water content and soil suction have the only corresponding relationship under unidirectional wetting and drying path, the time needed for wetting front formation can be seen as the absolute value of time differences between water content and suction wetting front point. Based on the Lumb formula of wetting front depth, the nonlinear correction expression is proposed subsequently by comparing the scatter distribution of wetting front measured and semi-empirical values.