Study on optimization of surrounding rock support in the predriven roadway during final mining of an extra thick coal...

To address the challenges of surrounding rock control in pre-driven roadways during the final mining stage of extra-thick coal seams, this study focuses on the 13,104 working face at Ciyaogou Coal Mine as a research background. Combining theoretical analysis, numerical simulation, and field engineering validation, the investigation examines stress distribution patterns, plastic zone evolution characteristics, and optimized support technology for surrounding rock under different lateral pressure coefficients (λ ≤ 1.0). Research findings reveal that: under varying lateral pressure conditions, circular roadway plastic zones predominantly develop three morphological types circular, elliptical, and butterfly-shaped. Roadway shoulder zones serve as the core areas for damage concentration, with failure progressively extending toward both sides. As the working face mining, peak stress primarily concentrates in the solid coal side's secondary influence zone of the main pre-driven roadway, with plastic failure severity escalating from 20 to 96%. Plastic zones in the roadway roof and floor transition from the residual pillar side toward the protective pillar side. Side deformation significantly exceeds roof-floor displacement, demonstrating distinct zonal asymmetric failure mechanisms. Consequently, a partitioned asymmetric support system incorporating "solid coal single-anchor cable + coal pillar anchor cable truss and channel steel anchor cable" is proposed. Field applications demonstrate effective control of main roadway roof-floor and sides convergence within 200 mm, with anchor cable stresses remaining below yield limits. This study provides an effective technical solution for surrounding rock stability control in pre-driven roadways during the critical final mining stage.