Study on Fluid‐Solid Coupling Simulation and Comprehensive Treatment of Coal Gangue Pile Slope Slip Process Induced by Rainfall Infiltration

ABSTRACT As a loose, engineered deposit with multiple terraces and a wide grain size distribution, coal gangue piles exhibit stability characteristics that differ from those of conventional rock and soil slopes. This study focuses on the gangue pile at the Min'an Coal Mine in Guizhou and employs a CFD‐DEM fluid‐structure interaction numerical simulation method to investigate the mesoscale mechanical mechanisms underlying rainfall‐induced slope slippage and instability. The study reveals that under rainfall infiltration, internal cracks in the slope exhibit a spatial distribution characterized by high density at the toe and low density at the crest. The initiation angles of micro‐cracks closely align with the macro‐scale slip direction and tend to propagate along existing fracture planes. By the time the simulation reaches Step (50 × 10 ⁴ ), the maximum particle displacement reaches 20.16 m, triggering a pull‐type failure mode that propagates downward from the crest. Detailed stress analysis indicates that the toe is the most mechanically sensitive region of the stepped slope. Rainfall infiltration causes a sharp decrease in effective interparticle contact force chains in this area, resulting in severe fluctuations in stress for both coarse and fine particles and a sudden increase in shear stress, which ultimately induces skeletal instability. This study conducted comparative simulation verification on a coal gangue mountain that had undergone comprehensive remediation. The results show that the slope maintains long‐term stability even under prolonged heavy rainfall. This study provides valuable insights for the management and stability analysis of similar coal gangue pile slopes.