Parameter optimization of coal face blasting for coal and gas outburst control

Coal and gas outbursts represent a major risk in deep gassy coal mines, and de-stress blasting is a commonly applied technology to prevent coal face outbursts. This paper systematically studies the effects of different parameters on de-stress blasting performance. The ultimate goal is to identify optimal parameters (blasting coupling medium, detonation position, and blast hole spacing) to enlarge the stress relief zone and reduce the risk of outburst. Initially, comparative 3D numerical models were developed using ANSYS LS-DYNA to study parametric sensitivities based on the conditions at the #8 coal mine in the Pingdingshan coalfield. We found the blasting power is greatly improved when the blast hole is filled with water, and the blast wave transmission towards the hole packer is greatly reduced. Forward blasting can promote transmission of the blasting wave deeper in the coal seam, which can increase the length of the stress relief zone in front of the coal face. The theoretically calculated cracking radii of water-coupled and air-coupled blasting were consistent with the simulation results. Additionally, an experimental system built for this study was used to verify that water-coupled blasting is preferable to air-coupled blasting, as predicted by the simulations. Ultimately, the optimized approach of water-coupled forward blasting with 6 m hole spacing was applied in an active coal mine, and the risk of outbursts was observed to reduce.