Study on the mechanical properties and fracture evolution laws of fractured rock under coupled effects of rainfall infiltration and mining-unloading

Due to the impact of rainfall, infiltration of rainwater into rock masses leads to an increase in their moisture content and pore water pressure, resulting in rapid evolution, expansion, and connectivity of existing joint surfaces within the rock mass. Additionally, coupled with mining-induced unloading, this phenomenon significantly triggers slope disasters. Taking the Dexing Copper Mine in Jiangxi province as a background, numerical simulations of fractured rock samples under different moisture conditions and pore water pressures were conducted using the Particle Flow Code (PFC). The results indicate that: ①With increasing moisture content, the compressive strength of the rock gradually decreases, with a reduction of 56.33% observed in saturated rock. Significant lateral expansion deformation was noted, with an increase of 69.06%. The rock exhibited pronounced tensile cracking characteristics, and the failure mode transitioned from tensile to shear failure. ② As pore water pressure increased, the compressive strength of the rock decreased, with a reduction of 21.74% at 2 MPa pore water pressure. The cohesive forces between rock particles weakened, leading to localized stress concentration, primarily manifested by the expansion and connectivity of pre-existing fractures in the rock. The research results can provide essential theoretical support for slope mining and surrounding rock reinforcement, ensuring the safety and stability of mine slopes.