Experiment research on the control method of automatically retained entry by roof cutting pressure relief within thick hard main roof longwall top coal caving panel

To address the large deformation of goaf-side entries resulting from intense dynamic pressure, a method involving automatically retained entry by roof cutting pressure relief (ARERC) technology is proposed for use in thick and hard main roof longwall top coal caving (THLTCC) panel. Both physical and numerical model experiments have been conducted to verify the effectiveness of ARERC technology in controlling deformation. The evolution laws of stress and deformation in the surrounding rocks of the retained entry and the mechanism of pressure relief by roof cutting are analyzed. Results indicate that this technique optimizes the roof structure of the roadway and interrupts roof stress transfer between the retained entry and goaf. Consequently, the maximum vertical stress on the roof-cutting side of the retained entry roof is generally lower than on the uncut side. The retained entry deformation undergoes four distinct stages behind the panel: the pressure relief stage, deformation stage, compaction stable stage and stabilization stage. Notably, the deformation stage exhibits the highest deformation rate for the roadway. Therefore, it is recommended to utilize single hydraulic props for temporary support during the deformation stage to prevent damage to the retained entry caused by dynamic pressure disturbance. Based on the above analysis, several recommendations are provided for the field application of ARERC technology. Finally, the results from engineering application show the effectiveness of ARERC technology in controlling the deformation of the goaf-side entry. This ARERC technology can be extended to other coal mines with similar geological conditions.