Optimization of Goaf Gas Drainage Parameters Based on Numerical Simulation Studying Fracture in Overlying Strata

Underground coal seam mining can redistribute the stress of the coal and rock, in which gas distribution and migration occurred. In order to draw out the gas in the goaf effectively, reduce the goaf gas emission and avoid the over ranging, the high level drilling site is employed for goaf gas drainage, and rock crack development situation and gas enrichment area are simulated by RFPA2D-Integrated to locate the position of drilling hole. The result indicated that the caving-in zones and fracturing zones of the coal cave mined out area are 0-13m and 13-42m to the roof of the coal, respectively. The optimal position of drilling hole is 14-35m. The practice survey revealed that the overall quantity of gas extraction is 8.47m3/min, and it solves the problem of goaf gas emission better. The result of simulation is accord with the field.