Model test study on rainfall-induced gravelly soil landslides

Under the background of frequent extreme rainfall, rainfall-induced gravelly soil landslides have become a major disaster type in the mountainous areas of Southwest China. To systematically reveal the deformation mechanism of landslides with different gravel contents under the combined action of rainfall and groundwater level, this study employs laboratory model tests. Four gravel content scenarios (10%, 20%, 30%, 40%) are simulated to analyze the variation laws of volumetric moisture content, pore water pressure, earth pressure, and deformation displacement. The study investigates the evolution patterns of landslides under different conditions and verifies the findings through field case comparisons. The results show that with the increase of gravel content, soil porosity and permeability coefficient increase, the peak values of volumetric water content and pore water pressure decrease significantly, earth pressure increases, and the overall sliding risk reduces. The earth pressure at different positions of the landslide shows different responses: the earth pressure at the rear and central zones first increases and then gradually stabilizes. Meanwhile, with the increase of gravel content, the failure mode of the landslide changes from a composite evolution mode of frontal traction and rearward thrust to a typical traction evolution mode. The conclusion of the model test are consistent with field cases, confirming that gravel content is a key parameter affecting the evolution path of landslides, which provides a reference for the early identification, stability evaluation, and treatment of gravelly soil landslides under high groundwater conditions.