Snowmelt and rainfall-induced slope failure mechanisms and post-failure behavior in Yili Valley, Xinjiang

In seasonally frozen regions, the interaction of snowmelt and rainfall infiltration during seasonal temperature transitions plays a critical role in triggering soil slope failures. These landslide events pose substantial risks to human life and infrastructure, underscoring the need for a better understanding of the failure mechanisms and post-failure behavior associated with snowmelt- and rainfall-triggered landslides. The Yili River Valley in Xinjiang, China, offers an ideal environment to study these processes. This study combines detailed field surveys, meteorological data analysis, laboratory testing of landslide material, and numerical simulations using the Material Point Method to analyze a representative high-level loess landslide in the area. The results reveal that initial crack formation at the toe of the slope, observed during the early snowmelt season, facilitates snowmelt infiltration. This infiltration, alongside rainfall, increases the pore water pressure, progressively reducing shear strength and slope stability. Ponding water in these cracks enhances hydrostatic pressure, further destabilizing the slope. Our post-failure analysis reveals that the frozen state temporarily stabilizes the slope by enhancing soil stiffness, but this stability is short-lived. During the transition to full saturation, driven by both snowmelt and rainfall infiltration, the slope’s resistance decreases significantly, with critical stress concentrations observed at the toe, indicating a regressive landslide failure mechanism. Strain and displacement analyses demonstrate that the frozen state reduces these values by 43% and 50%, respectively, temporarily enhancing stability. However, during full saturation, strain surges by 76% and displacement by 144%, marking an elevated risk of slope failure. This sequence highlights the dynamic impact of seasonal moisture variations on slope stability, emphasizing the critical need for continuous monitoring and targeted slope stabilization strategies in freeze-thaw environments.