Research on Failure Mechanism of Bottom Coal Pressure Relief of Thick Coal Seam Based on Numerical Simulation

In view of the problems of large residual thickness of bottom coal, large blasting engineering quantity, low pressure relief efficiency and others during the continuous mining and filling process of the 1301 working face in Gucheng Coal Mine, a coupled structure model including bottom coal-surrounding rock is constructed based on FLAC^3D numerical simulation software. Mohr-Coulomb constitutive model and transient blasting load theory are adopted to simulate and analyze the influence law of blasting parameter changes on fissure expansion path and pressure relief effect. On this basis, an optimized blasting parameter combination with a charge weight of 1.8 kg, hole spacing of 0.8 m, and row spacing of 3 m as the core is proposed to construct a directional control type pressure relief technology system. The on-site test results show that the optimized scheme reduces by over 31% in aspects of blasting hole number, construction footage, and dynamite consumption compared to the conventional process. The decrease in bottom coal stress is improved by 42.7%, and the surrounding rock displacement is reduced by 42.5%, a dual improvement in pressure relief effect and construction efficiency is achieved.