Experiment Study on Pre-cracking Blasting and Permeability Improvement Effect with Deep Borehole for Seam Opening of Crosscut

According to the difficult borehole gas drainage in the low permeability outburst seam, the slow seam opening speed of the crosscut and other problems, the paper had a study on the outburst prevention mechanism of the pre-cracking blasting and permeability improvement with the deep boreholes in the low permeability seam.With the theoretical analysis, the research and development of the deep borehole pre-cracking blasting explosive cartridge and the site test combined method, th e pre-cracking blasting vibration radius with the deep boreholes in No.5-2 seam of the Dongsi district B group of a mine in Huainan Mining Area was measured.Based 0 n the parameters, the gas drainage boreholes and the blasting boreholes in No.5-2 seam were optimally designed.The results showed that after the pre-cracking blastin g and permeability improvement technical measures with the deep boreholes completed in the low permeability outburst seam, the elastic potential of the seam was effe ctively released, the gas pressure gradient of the seam was reduced and the excitation outburst stress was effectively eliminated.The permeability coefficient of the sea m was increased by 123 times and the pure quantity of the gas drainage from the seam was improved by 69 times higher than before the blasting operation completed. The seam opening time of the crosscut was highly reduced and was only 47 days which was reduced about two months faster than the seam opening time with the conv entional seam opening method and could ensure the normal replacement of the mining and excavation operations.