Effect of principal stress rotation on the stability of a roadway constructed in half-coal-rock stratum and its control technology

Engineering disturbance-induced adjustment of the stress field in the surrounding rock is the main reason that leads to dynamic disasters in deep rocks. This study selected the mining roadway in the No. 92125 working face of the Chacheng Coal Mine as the engineering background for in-depth and systematical analysis on the principal stress path and the changes in the principal stress direction of surrounding rocks under excavation-induced disturbance and the resultant damages. Results demonstrate that the fracture planes were along the direction of intermediate principal stress under true triaxial tests and the internal cracks in the rock strongly depend on the direction of the intermediate principal stress. Therefore, variations in the stress path of the roadway surrounding rocks can cause dramatic changes in their fracture characteristics (direction of rupture). The same results were found for the analysis: the variation of the direction of principal stress on the surrounding rocks in the roadway created adverse effects, which thus triggered great damages. The areas of roof and the shoulder angle, etc. were strongly affected by the principal stress rotation, and the damage caused was obvious. According to the damage characteristics of the surrounding rocks caused by the principal stress rotation during excavation in half-coal-rock roadway, the idea of strengthening support in key areas was proposed, and a high-strength pre-tension support scheme using anchor beam, nets, and cables was proposed. Finally, field measurement results of displacement on the surface and in surrounding rocks reveal that using the optimized supporting scheme effectively controlled deformation in the roadway, ensuring stability of the roadway and meeting engineering requirements.