Abstract:To reveal the instability mechanism of mine slopes under the combined action of earthquakes and rainfall, this study takes a mine slope in Gejiu, Yunnan as the object, and based on the GeoStudio platform, couples the limit equilibrium method and Mohr Coulomb model to construct a numerical model of unsaturated soil seepage slope stability. Research and improve the logic of transferring residual deformation from earthquakes to initial rainfall conditions, verify the effectiveness of the model through on-site monitoring, and conduct sensitivity analysis of multiple operating conditions and geological parameters. The results showed that the seismic amplification effect caused a sudden increase in the acceleration at the top of the slope, triggering a tensile stress failure of 0.5-1MPa. The increase in pore water pressure led to a decrease in shear strength, and the safety factor fluctuated between 1.33-1.62. The slope entered a critical state, and the horizontal displacement of the collapsed layer and debris area exceeded 0.7m. After the earthquake, rainfall brought in infiltration along the earthquake loosening, increased water content, reduced matrix suction, and delayed the dissipation of excess pore water pressure, weakening the stability of the collapsed layer and strongly weathered layer; Under the synergistic effect of the two, the slope safety factor fell below the critical value of 1.3 on the 5th day, triggering the sliding instability of the landslide layer and artificial accumulation along the interface. Sensitivity analysis shows that shear strength parameters are the main controlling factors under earthquake conditions, while permeability coefficient and rainfall intensity play a dominant role under rainfall conditions. Geological fracture zones and strongly weathered layers are sensitive strata. Research provides support for the safety assessment and disaster prevention of mining slopes.