An improved Green-Ampt model for rainfall infiltration analysis of multi-layered heterogeneous soil slopes

The rainfall infiltration analysis of slopes is of a great significance to the reinforcement design, mitigation and risk mitigation of rainfall-induced landslides. The classical Green-Ampt model, whose parameters have clear physical meanings and which is easy to implement, ignores the fact that a transition layer objectively exists in infiltration zone. It cannot effectively analyze the rainfall infiltration process of multi-layered heterogeneous slopes considering the spatial variability of hydraulic conductivity. To this end, an improved Green-Ampt model is proposed for the rainfall infiltration analysis of multi-layered heterogeneous slopes, and it considers the elliptical transition layer of rainfall infiltration and evaluates the water content distributions under different rainfall durations. Additionally, an infinite slope model is taken as an example to validate the effectiveness of the proposed improved Green-Ampt model through four common slope scenarios. The corresponding slope stability analyses under rainfall infiltration are also conducted. The results indicate that the distributions of volumetric water content and the factors of safety evaluated using the proposed model are well consistent with the numerical results of Richards' equation for these four slope cases. In contrast, the modified Green-Ampt model produces the biased distributions of volumetric water content and smaller factors of safety. In addition, the location of the critical slip surface of the slope can be accurately identified using the proposed improved Green-Ampt model. The research outcome provides theoretical references for the rainfall infiltration analysis of multi-layered heterogeneous soil slopes and the reinforcement design and risk control of rainfall-induced landslides.