An improved Green-Ampt infiltration model of depth-dependent initial soil water content and its experimental verification

Rainfall infiltration analysis is essential for evaluating slope stability. Conventional Green-Ampt models assume homogeneous soil or presume specific functional forms of the initial water content distribution, limiting their applicability to heterogeneous slopes. To overcome this limitation, this paper proposes a generalized improved Green-Ampt model that accommodates arbitrary distributions of initial soil water content by numerically solving the governing equation with the Newton-Cotes formula, and further incorporates the moisture-driven variation of hydraulic conductivity during infiltration. The model is validated through an indoor rainfall infiltration experiment on a physical slope model monitored by the high density electrical resistivity tomography (ERT). The results show that the depth-dependent distribution of initial soil water content governs the water storage capacity, whereas the moisture-driven variation of hydraulic conductivity mainly affects the seepage process after the onset of surface ponding. The calculated wetting front depths agree well with the experimental measurements, confirming the accuracy of the improved model and extending the Green-Ampt framework to practical rainfall infiltration analyses of slopes.