Effect of Pressure Relief Hole Spacing on Energy Dissipation in Coal Seam at Various Mining Depths

The large diameter pressure relief borehole is one of the most effective technical means to prevent and control rockburst during deep mining. Based on the engineering background of rockburst mines, the mechanical model of coal energy dissipation of large diameter pressure relief holes is established by theoretical analysis, and the approximate formula for calculating energy dissipation of coal is obtained. Combined with numerical simulation methods, the energy accumulation and dissipation laws of coal under various mining depths and the various spacings of pressure relief holes is studied. The results show that the upper and lower ends of the pressure relief holes have the highest degree of energy dissipation and the largest range of energy dissipation. While the energy dissipation effect on the left and right sides of the pressure relief holes is poor, a high accumulation of elastic strain energy occurs at a certain distance on the left and right sides of the relief holes. The dissipated energy of the coal seam increases continuously with the increase in mining depth and the decrease in spacing of pressure relief holes. The dissipated energy rises especially suddenly when the hole spacing changes from 1.0 m to 0.5 m. For coal seams with high rockburst risk, the spacing of pressure relief holes can be set to be less than or equal to 0.5 m, which can greatly improve the energy dissipation effect of coal seams. The studies can provide a theoretical basis for the optimization parameters of pressure relief holes for rockburst prevention.