Instability mechanism of loess-mudstone landslides under rainfall infiltration conditions

The evolution of seepage field in large loess-mudstone landslides is significantly influenced by rainfall infiltration, which is a critical factor affecting their stability. This paper presented a case study of the Hongya Village landslide in Huzhu County, Qinghai Province, to better understand the impact of rainfall infiltration on the triggering mechanism of loess-mudstone landslides. A combination of field investigations, high-density electrical resistivity surveys, and numerical simulations was employed to systematically analyze the temporal and spatial distribution of pore water pressure, volumetric water content, and shear strain within the landslide mass under rainfall infiltration conditions. The results indicated that the rainfall infiltration markedly alters the seepage characteristics of the landslide mass, leading to a sharp increase in pore water pressure and a significant reduction in shear strength, which consequently reduced the overall stability of the landslide. The stability analysis identified a stepwise instability process in the landslide, characterized by "shear displacement-tensile failure-pulling effect" triggered by rainfall infiltration. The findings provide a comprehensive understanding of the instability mechanisms of loess-mudstone landslides under rainfall conditions, thereby offering valuable scientific guidance and technical support for the prevention and mitigation of similar landslide hazards.