Abstract: In order to understand the influence of steep seam mining on the surrounding rock mass in complex structure, the mining process has been simulated based on PFC^3D of particle flow. The coal seams are in synclinal left with horizontal fracture, and coal seam dip angle is 87°. Simulation scheme has been divided into 11 cycles, and the simulated mining depth is 240 m. This paper has analyzed the damage characteristics of rock mass in the excavation process, and put forward some possible measures. Simulation results have shown that the right side of rock mass of 40 m wide mined-out area is the most stable area. The left side of the rock mass dumps to the left before bending to the right. The left side of the rock mass of 30 m wide mined-out area is stable; the right side of the rock mass damage is the most serious. The mass between two mined-out areas is left dumping, leading to obvious subsidence in this part of surface. Before 30 m wide coal mining, rock mass on the right side should be reinforced, or the level constraints be imposed on rock mass; and the right side of rock mass of 40 m wide may not be reinforced.

Key words: coal mining, steep seam, simulation mining method, analysis of rock migration, particle flow