Deformation Mechanism and Control Ttechnology of Surrounding Rock of the Roadway in a Steep Coal seam

This study combined theoretical analysis, numerical simulation via FLAC3D software, innovative design, and field measurements for establishing the mechanical model of the stressed coal rock and deriving the deformation and failure characteristics of the roadway in a steep coal seam. The No. 49# steep-seam working face of the Xintie Coal Mine, China, was used as a case study with asymmetrical force characteristics of the mining roadway. The roof and the right side of the roadway under study were identified as the main deformation and failure zones in the roadway of the steep working face. Next, a rigid/flexible support method that fully enclosed two sides and the roof was designed and substantiated. It comprised three pre-stressed resin anchor cables combined with anchor rods, iron net, and steel bands for the roadway roof support; besides, three anchor rods were combined with iron net and steel bands for supporting the right side of the roadway. A novel self-mobile forepoling hydraulic support group with side and roof support functions was developed. A grouting reinforcement was applied to the crushed coal rock in the geologic anomaly zone to enhance the overall performance. Finally, the measured displacements of the roof and the floor were found to exceed those of the roadway sides. The whole advancing process of the steep-seam working face was conditionally split into three segments, namely, Segment I with no mining effect (at a distance over 50 m from the working face), Segment II with a mining effect (at 20 ~ 50 m from the working face), and Segment III with a strong mining effect (20 m in front of the working face). The displacement at the deepest point on the roof was the maximal, followed by that in the range of 0 ~ 1.5 m, which made it possible to reduce the number of anchors on the left side of the roadway required by the conventional symmetric support mode. The performed field measurements proved that the proposed asymmetric support mode ensured the mining safety requirements of the working face under normal mining operations, being more cost-effective and efficient than the conventional symmetric one.