Stability Analysis and Failure Control of Composite Roof in Mining Roadway Considering Plastic Zone Expansion

To address the problems of the large deformation of surrounding rock, failure of support, and even roof fall under the influence of severe mining in the return airway of the panel I0116³06 in Mindong No.1 Coal Mine, the fracture evolution characteristics and deformation law of the roadway composite roof were investigated through numerical simulation, theoretical analysis, and on-site detection. With the continuous evolution of the magnitude and direction of the main stress in the surrounding rock of the mining roadway with a composite roof, the following observations were made: first, plastic failure occurred in the shallow area; second, because the undamaged hard coal seam cannot block the expansion of the plastic zone, the plastic zone crosses the undamaged hard coal seam and expands into the deep part. The strong deformation pressure caused by the expanding plastic failure of the deep interlayer leads to tensile fracture failure at the middle of the lower part of the undamaged hard coal seam, and to overall instability. According to the evolutionary pattern of the plastic zone in the composite roof of the mining roadway, the multi-level coupling support technology (MCST) focusing on the fracture morphology of the composite roof is applied to the test roadway. The field monitoring results reveal that the application effect is satisfactory.