Rainfall infiltration process of multi-layer slope based on improved Green-Ampt model stability analysis

Under the effect of rainfall, the saturation and water content of slope soil increase, while the matric suction decreases. With the increasing rainfall duration, rainwater infiltration depth has an effect on slope stability. However, the traditional infiltration calculation method of slope with the multi-layer structure does not consider the matric suction and the formation of inter layer water points that change with the infiltration depth, and ignores the influence of part of rainwater flowing along the slope layer in saturated layer on the infiltration process. The variation of the location of potential sliding surface with the rainfall duration is also not considered. Therefore, in this paper, the infiltration process is decomposed into several sub-processes, and the infiltration calculation method of traditional multi-layer slope is improved based on the Green-Ampt (G-A) infiltration model to solve each sub-process. The solutions of sub-precesses are finally merged into the solution of the whole infiltration process. The formation time of interlayer water point is calculated, the relationship between rain water infiltration depth and time is analyzed, and the influence of rainfall intensity and rain water infiltration depth on stability coefficient and sliding surface position at different positions of slope (wet front, saturated layer) is also studied. The results show that (1) the results obtained by the improved calculation method based on the G-A model are closer to the numerical simulation results than those obtained by the traditional multi-layer structure slope infiltration calculation method. (2) For the soil slope with multi-layer structure, its safety factor decreases with the increasing rainwater infiltration depth, and the phenomenon of mutation occurs when the interlayer water point is formed. (3) With the increasing rainfall duration and rainfall intensity, the position of the potential sliding surface in the slope change. The potential sliding surface appears at the humid front in the early stage, and at the interface of the saturated layer in the later stage. This method improves the accuracy of the traditional rainfall infiltration calculation method of the multi-storey structure slope, makes a more comprehensive evaluation of the stability of the multi-storey structure slope, and further expands its engineering application scope.