Research on rapid tunneling technology for enhancing permeability and eliminating outburst in high gas seam based on CO₂phase change fracturing

In order to effectively solve engineering problems of gas outburst, poor permeability of coal seam, unqualified extraction effect and slow speed of rapid roadway excavation in 11009 working face of Pingshan Coal Mine, influencing factors of rapid roadway excavation are summarized and analyzed, and cracking anti-reflection and rapid roadway excavation technology by liquid CO₂phase change is proposed.The principle of cracking and anti-reflection technology is presented, the extraction technology scheme is optimized, and technical parameters and effect evaluation indexes of cracking anti-reflection technology by liquid CO₂phase change are determined.The industrial test results show that by arranging 20 fracturing rods with a diameter of 94 mm, each of which is filled with 1.5 kg of liquid CO₂, and is arranged along the roadway heading direction along the seam, the gas drainage concentration of the borehole after the coal seam fracturing is maintained above 40% for a long time, the gas concentration of the roadway return air flow is stabilized within 0.3%, the coal seam gas content is reduced by 6.09 m³/t on average, the maximum reduction is 58.83%, and the gas treatment time per hundred meters of roadway heading can be reduced by 33 days.The gas drainage effect and roadway driving speed are significantly improved, effectively solving the engineering problems of poor gas drainage effect and slow roadway driving speed.