Study on numerical simulation of effective drainage radius of drilling hole in coal seam

A seepage-stress coupling model of coal containing gas was established considering effect of coal permeability changing on gas flow based on coal seam gas flow theory and elastic mechanic. The second development of COMSOL Multiphysics numerical simulation software was taken according to the model. A model of gas drainage model of drilling hole in coal seam was established taking a gas outburst mine as an example and resolved with numerical solution. The results show that coal seam gas pressure and coal permeability decrease gradurally with time extending, meanwhile effective radius of drilling hole increases gradually, and both have certain timeliness. The field test is taken by use of a pressure testing method with a result in accordance with the simulated one basically, which verifies correctness of the seepage-stress coupling model of coal containing gas and feasibility of calculating effective drainage radius of drilling hole by numerical simulation method.