Numerical Simulation of Gas Drainage with High-Position Boreholes Along Coal Seam

In the coal seam 19 of Baliancheng Coal Mine,the 62.1%～71.6% of gas emission was from goaf.A gas drainage procedure with high-position boreholes along seam in goaf was proposed in order to control the gas disaster.Based on the key stratum theory and the "O" shape circle theory,fissure pattern in the overburden rock strata above the goaf was analyzed.Through the study of the gas migration in overburden rock fissure,it is regarded that the gas flow follows the Darcy's law.A numerical simulation was done with the commercial software COMSOL-Multiphysics for gas drainage.It clearly illustrated the gas migration during the flow drainage.The results showed that the gas drainage reduces the gas pressure effectively.This study may provide theoretical basis for site gas drainage and is of important practical significance.