Evolution and Stress Distribution of Overlying Strata in Deep and Thick Closer Coal Seam

Simulation experiments and theoretical calculations are conducted with reference to Haishiwan Coal Mine to solve such problems as excessive deformation and sudden pressure increase in the coal seam and the roadway during the coal mining process in deep wells. The evolution and movement of the overlying strata structure caused by the mining of the coal seams at similar distances were simulated and analyzed. The results show that whether the main key layer in the overlying strata is unstable or broken has a significant impact on the pressure distribution. Before the main key layer breaks, the near-field structure is the main source of rock pressure increment and volatility. After the main key layer is broken, the far-field structure plays a major role in increasing the pressure of each close coal seam and causing the jumpy increase of pressure. The evolution of the overburden strata that spreads from bottom to top causes the subsidence of the main key layer, which plays a major role in the jumpy change of the mine pressure. The knowledge of the law about overburden rock evolution and the mechanism of rock pressure during the mining of closer coal seams are of guiding significance for the ground pressure control and the optimization of roadway support.