Study on Pressure Relief, Pre-Splitting, Softening and Gas Extraction in Highly Tough and Extra-Thick Outburst Coal Seams with Hard Roofs: A Case Study

Abstract

ABSTRACT With Yushutian Coal Mine as the engineering background, the feasibility of pressure relief, pre-splitting and softening (PPS) by adjacent seam mining and its impact on top coal caving and gas extraction were studied, and the technology was applied on site. Through theoretical analysis, numerical simulation and onsite investigation, the feasibility of using gob-side entry retaining technology to achieve continuous mining of adjacent seam (Lower 4# coal seam) for PPS of underlying coal rock was demonstrated. The onsite application result shows that after the mining of the Lower 4# coal seam, the periodic weighting step of the 110,504 working face is shortened by half; the goaf basically caves along with mining; and the maximum monthly mining rate rises to 97.3%. After high-level directional long boreholes gas extraction, the gas concentration in return air of the 110,504 working face declines to 0.3–0.35%. Through the application of PPS by adjacent seam mining, the mining rate of the working face jumps significantly, and the gas concentration drops notably. Meanwhile, the coal and gas outburst coal seam is recovered safely and efficiently. The above research serves as a valuable reference for the safe and efficient mining of coal mines and enhance gas energy utilization with similar geological conditions.