Multilayer Soil Infiltration Model and Infinite Slope Stability Analysis Considering Dynamic Correction of Infiltration Coefficient

The traditional Green-Ampt model inadequately characterizes unsaturated transition zones and interlayer infiltration discontinuities during rainfall infiltration in multi-layer slopes. This study extends an infiltration gradient-driven model by integrating a dynamically corrected transition zone infiltration coefficient with a layer control function to simulate interfacial discontinuities during wetting front propagation. Validated against theoretical models, soil column experiments, and numerical simulations, the proposed model accurately quantifies wetting front propagation and hydraulic gradient surges at low permeability interfaces that affect slope stability. Key findings include: (1) interface permeability contrasts regulate wetting front migration by inducing pore water pressure accumulation that reduces interface propagation velocity by 30%; (2) rainfall intensity (8 mm/h) amplifies shallow wetting fronts by 22.8%, while interface barriers attenuate deeper infiltration (>2.5 m) by 14.8%. Slope steepness (10° increase) reduces infiltration by 17.2% and stability coefficients by 12-15%. High initial moisture (θi = 1.4θe) reduces short-term stability by 37.8% compared to dry slopes. The improved framework provides a robust tool for evaluating the response of multilayered slopes to rainfall infiltration.