Study on stability and control of surrounding rock in the large section stopping space with extra-thick coal seam

The stability of the stopping space is an important guarantee for the efficient and safe withdrawal of coal mining equipment. The influence of the position of the main roof fracture line on the stability of the surrounding rock in the stopping space was discussed, and the reasonable un-caving coal distance for the final mining stage of the working face was determined through discrete continuous coupling numerical simulation analysis. The instability interval of the key block of the main roof above stopping space was obtained by mechanical theory. The results showed that: (1) The reasonable stopping position of the working face in extra-thick coal seams was that the main roof fracture line was located behind supports (LLBS), and the reasonable un-caving distance of top coal was 10 m. (2) When the un-caving distance of top coal was 10 m, the load above key block was less than the critical load of sliding instability and rotary instability, and the voussoir beam structure was stable. (3) Asymmetric support scheme indicated that the support effect of the roof above the retraction channel was stronger than that of the roof above supports. The observation of underground pressure showed that the stopping space was effectively controlled.