Application and Evaluation of "Quaternity" Outburst Prevention System in Lower Working Face Containing Coal Pillar

For the characteristics of stress concentration, high gas content and strong gas outburst of coal pillar zone from lower working face in Qudi Mine, coal pillar zone is the key management area by using comprehensive outburst prevention technique of "quaternity". Through regional pre-drainage by using hole drilled along seam, the maximum residual gas content in coal seam was 5.11 m³/t, which is located in coal pillar from working face, it was less than 8 m³/t that was critical index of outburst, the residual gas content in coal seam showed "convex" form along the direction of face advancing, which reflected the function about pressure relief, drainage and extraction; regional verification used gas desorption index of drill cuttings △h₂ and S, and △h₂ was 60 Pa to 80 Pa, S was 1.6 kg/m to 1.8 kg/m, which were all less than critical index of outburst. The gas density in return air was only 0.18% to 0.31% during the mining of working face containing coal pillar, it recovered 85 thousand ton coal, and saved cost 4.321 million yuan, the"quaternity"ensures safety and efficiency of working face mining.