Treatment technology for rock burst hazard zones in protected seam mining under close-distance coal seams

To mitigate the risk of rock burst in stress concentration zones induced by residual coal pillars after the extraction of the upper protective seam in close-distance coal seams,this study takes the No. 183 lower 06 working face of Jining No. 3 Coal Mine as the engineering background. A similar material simulation test was conducted to systematically investigate the overburden movement law during protective seam extraction,the stress influence range of residual coal pillars in the No. 3 upper coal seam,and the distribution characteristics of advance abutment stress during protected seam mining. The results show that the stress concentration zones of the No. 3 upper coal seam are mainly distributed within 6-38 m ahead of the working face stop line and 2-40 m behind the open-off cut. As the ming of No. 3 lower coal seam advances into the goaf of the No. 3 upper coal seam, the roof stress exhibits a three-stage pattern of “stress increase-stress release-stress recovery”. During the stress increase stage,the measuring points are within the influence range of the residual coal pillars of the upper coal seam,with stress levels higher than the in-situ stress and showing a gradual upward trend with mining disturbance. When the working face advances to about 4-14 m ahead of the stress monitoring point,the stress reaches its peak value,and the stress concentration coefficient is higher at points closer to the open-off cut of the No. 3 upper coal seam. As the working face continues to advance,the measured stress shows a downward trend and reaches its minimum value at 6-10 m after the working face passes the monitoring point. Thereafter,the goaf is gradually compacted, and the stress level progressively recovers to the in-situ stress. Pressure relief schemes for the stress concentration zones are proposed, including large-diameter borehole pressure relief and blasting roof cutting pressure relief. Field monitoring results demonstrate that the pressure relief schemes in the stress concentration zones achieve satisfactory effects and ensure the safe extraction of the working face.