Stability control of roadway surrounding rock with narrow barrier pillars in orthogonal mining layouts: numerical and field investigations

Abstract During the recovery of coal pillars in exhausted mines, strategic roadway planning is essential for enhancing coal extraction efficiency and addressing mining replacement challenges. This paper presents an innovative roadway layout designed specifically for longwall coal pillar recovery (CPR) face in narrow protected coal pillars subjected to repeated mining. A global numerical model for the 2217 tailgate of Shengping Coal Mine of Shanxi Province, China is established and verified. The evolutionary behavior of internal vertical stress, the plastic zone, and the energy response to coal pillar width variation during 2214 face advancement is analyzed. Maintaining the pillar width at 8.0 m results in a vertical stress maximum of 24.5 MPa, and the high-dissipated energy element ratio η is 0.894, suggesting the pillar core retains high bearing capacity. During excavation operations at the 2217 CPR face, an L-shaped stress concentration zone developed ahead of the face. The 8.0 m wide coal pillar rapidly failed under lateral abutment stress, reducing the peak vertical stress to 7.82 MPa. A control strategy combining stepped hydraulic fracturing and cross-grouting anchor cables was proposed and successfully implemented. Monitoring results indicate that surrounding rock displacement in the 2217 tailgate remains within a controllable range, meeting the requirements for safe and efficient production. This approach provides a novel solution for mining operations under similar conditions.