Instability evolution mechanism and collaborative control technology of high-stress fractured roadways

Addressing the support challenges of roadways with high-stress broken roofs during mining in the lower slice of thick coal seams. Taking the upper entry of the 14022 working face in Zhaogu No. 2 Mine as the engineering background, a roof mechanical model for the failure characteristics of broken surrounding rock under high-stress conditions was established. The stress distribution characteristics of the floor in an elastic state were obtained, and the rotational characteristics of floor stress distribution were clarified. The plastic zone equation of surrounding rock under a three-dimensional stress environment was derived, and the plastic distribution characteristics of roadway surrounding rock were obtained. The research results show that: under the disturbance of mining in the upper coal seam, the stress distribution of the surrounding rock exhibits significant directional deflection, with the principal stress direction changing markedly. This principal stress deflection leads to an obvious asymmetric distribution of the plastic zone in the surrounding rock, with the plastic zone concentrated in the roof and left rib of the roadway, inducing asymmetric failure of the surrounding rock. The combined effect of principal stress deflection and the fragmentation of the overlying strata is the fundamental cause of severe asymmetric failure of the roadway surrounding rock. Furthermore, due to mining disturbances, the floor of the overlying strata becomes broken, further exacerbating the failure degree of the roadway roof, resulting in anchor cable anchorage failure and a significant decrease in the support effect of steel sheds. Based on this, a new type of two-component grouting material was developed, and a combined support scheme of “grouting reinforcement + asymmetric anchor cables” was proposed. Field application shows that the deformation of the roadway roof and floor decreased by 36%, and the deformation of the two ribs decreased by 51%, significantly restraining surrounding rock deformation and improving roof stability, providing a reliable technical reference for roadway support under similar conditions.