Numerical Modeling on Loosening Blasting in Coalbed to Enhance Gas Drainage

The coal seam methane poses a serious threat to production equipments and personal safety in underground coal mining of China. Loosening blasting is one of the most important measures to enhance gas drainage in coal seam and to prevent gas outbursts. In this work, a coupled multiphysical model for the blasting damage of coal and gas flow in coal seam is proposed, based on which the evolution of damaged zone and release of stress concentration in coal seam before and after blasting near the working face is examined by means of numerical simulation according to an actual in situ condition during underground coal mining. The numerical simulation indicates that, after the loosening blasting in coal seam, a broken zone with radius of 1.0 m and a loosening zone with radius of 1.2m are formed around the blasting hole. Moreover, due to the loosening blasting, the stress concentration area above blasting hole is extended from � = 3~4 m to � = 7~10 m deep into the coal seam, while that above the controlling hole is extended from � = 3~4 m to � = 4~8, thus confirming that the loosening blasting has notable effects on increasing coal bed permeability and enhancing gas pre-drainage. Keywords: Coalbed, loosening blasting, gas drainage, numerical modelling