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Fracture of a critical stratum on a coal seam roof may cause strong strata pressure behaviours. In particular, a large-scale sudden fracture of the critical stratum, which is formed by hard thick sandstones on a mining face with a large mining height, can easily cause dynamic disasters of wells. In this study, a simulation analysis of the deformation and failure laws of a hard thick roof in an island mining face with a large mining height in Xinji 2# Mine 210106 after the mining of Coal bed A1 was performed in accordance with the occurrence characteristics of sandstones. Results demonstrate that large-scale fracture suddenly occurs at a gob roof after the working face is advanced by 120 m. A mechanical analysis model of the island working face was constructed. This model comprises 17.9 m of fracture on the 16 m thick sandstone roof. Hydraulic support provides 16854.1 kN of supporting resistance to maintain the stability of the rock beam and thus prevent threats to the supporting devices of the working face. The hard thick roof was weakened every 15 m in the transport gateway and air return in advance through an advanced deep-hole pre-splitting blasting technique. In accordance with the measurement results of underground pressure, the forced caving of thick sandstones relieves the influence of roof loads on the support and thus realizes safe mining.