Roadway roof shear slip movement mechanism induced by the strong dynamic pressure while ultra-thick coal seam mining

To clarify the roof shear slip movement mechanism of roadways subjected to strong dynamic pressure during ultrathick coal seam mining, this study investigates the return airways of the 5107 fully mechanized top-coal caving (FMTC) panel at Yushupo Mine as a case study. The deformation characteristics and structural instability of surrounding rock in high-stress roadways were systematically analyzed through field observations, theoretical modeling, numerical simulation, and engineering verification. Based on the limit equilibrium theory, a dynamic pressure thick coal seam roadway roof shear slip mechanics model was established, and the spatial distribution of the shear slip zone and the minimum effective anchorage thickness were quantitatively determined. A new integrated collaborative control strategy of "bending resistance shear control displacement" was proposed for ultra thick coal seam roadway, and on-site practice was carried out. The results indicate that the roof shear slip surface initiates approximately 0.53 m from the roadway rib, propagates toward the centerline, and reaches its maximum development at a height of 4.58 m, located only 0.06 m from the centerline. The pronounced reduction in safety factors near the centerline reveals a critical zone highly susceptible to roof instability induced by strong mining-induced dynamic pressure. Discrete element method (DEM) simulations were employed to quantify the effects of key controlling parameters, including roof coal cohesion, parting layer position, and support configurations, on the evolution of roof shear slip movement. On this basis, a coordinated control strategy integrating bending resistance, shear strengthening, and displacement control was proposed. A full-length anchored cable reinforcement scheme tailored for ultrathick coal seams was developed and implemented in the field. Monitoring results demonstrate that the proposed support system effectively controls surrounding rock deformation, optimizes bolt-cable load transfer, suppresses bed separation, and significantly enhances roof stability. Field application confirms its effectiveness in mitigating large deformation in surrounding rock and ensuring the safe and efficient mining of ultrathick coal seams.