Experimental Study on Loosening Radius of Pre-drainage Borehole by Pre-splitting Blasting for Increasing Permeability at 2306 Working Face of Zhangcun Coal Mine

Zhangcun Coal Mine is a high gas mine. The low permeability of coal seam causes the low gas extraction rate and mining safety hidden trouble. So, the technical measures of deep hole control pre-splitting explosion are provided to improve the coal seam permeability in coal mine. The technical measure of deep hole pre-splitting explosion in underground coal seam is provided in 2036 working face of Zhangcun Coal Mine. According to the blasting test in different borehole spacing that was selected between the control hole and the blasting hole at the scene, researches find that pre-splitting explosion can improve the permeability effectively in 2036 working face. Gas concentration improves 3 times mostly than that of the coal mine without blasting, the gas quantity increases 4 times mostly, and the amount of coal mine methane drainage significantly increased. When the borehole spacing between the control hole and the blasting hole is 4 m, the amount of coal mine methane drainage is the biggest, the attenuation is the slowest and the extracting result is the best. So, 4 m is the loosened radius of coal seam in 2036 working face of Zhangcun Coal Mine.