Action of control holes on deep-hole blasting in outburst coal seams

In order to explore stress wave propagation and action of control holes for deep-hole blasting in coal seams, based on parameters of blasting, explosive and coal mass got from the Songzao coal and electricity company, a numerical simulation model of linear charge blasting in coal seams was built by means of 3D numerical simulation. The stress propagation feature and effective area of gas drainage by blasting action were analyzed in the soft coal bed with the control holes. The study indicate that the average effective stress in boundary of the control holes which are constructed before blasting is 48%~66% higher than that at the same location without control holes. With the increase of the distance between the blasting hole and control holes, effectives stress decreases in coal seams, but average stress ratio at the same locations with and without control holes increases. Simulated results are in agreement with the gas draining data got from the coal mine before and after blasting. It is necessary that the control hole is pre-arranged before detonation.