Study Of Deep-hole Presplitting Blasting Increasing Permeability On High Metamorphic Outburst Coal Seam

High metamorphic has more outburst danger due to its huge gas content and strong adsorption. Dense fracture of coal structure rank cause gas is difficult to be desorbed, which is hard for gas extraction and extraction pure volume. Also, it limits the speed of the excavation working face and the engineering time of rock cross-cut coal uncovering. Therefore, a timely problem should be solved to enhance the permeability of high rank coal seam, improve the gas drainage rate and eliminate the gas outburst danger of high metamorphic coal seam.Firstly, this paper studies industrial group, fracture characteristics of the high rank coal, focusing on analysis of the influence of coal metamorphic degree of pore fracture system on gas occurrence. The paper also determines gas content and permeability coefficient of high metamorphic coal seam.At the conclusion of theory on the basis of deep-hole presplitting blasting, blasting action principles are analyzed. Elaborating the effect of detonation energy, stress wave, control hole, explosive gas and gas pressure is on the process of blasting crack. The conclusion is detonation energy is the main reason for smash circle forming and the range of stress wave is the main area of coal and rock failure. Explosive gas and gas pressure will form stress concentration in the crack tip, which can promote the crack expansion.Using explicit dynamic analysis software LS-DYNA to simulate the coal body in deep-hole pre-splitting blasting process, models suitable for the actual conditions are established. According to analyzing stress cloud atlas, fracture and effective force curve, the results show that the control holes blasting play the role of guidance and compensation. And the distance of 4-6m between blasting holes can produce more cracks in the coal and rock mass for good blasting effect.Tests carried out in the working faces of the 1805 excavation and the 1805 rock cross-cut coal uncovering in the Wulunshan coal mine has good effect. Deep-hole presplitting blasting can increasing the permeability of coal,improve the gas drainage concentration and pure quantity and reduce the gas content of coal. It is a positive and feasible scheme on high metamorphic coal seam for preventing the overrun of outburst danger in the working faces.