Practice and application of mine tremor prevention and control for vertical well fracturing in hard thick roof

To investigate the effectiveness of surface vertical well fracturing technology in preventing and controlling mine tremors at deep, high mine pressure working faces, a case study was conducted at the 20103 working face of Dahaize Coal Mine. The control effect was verified by analyzing the pressure curve variations and fracture development extent during fracturing, as well as the periodic weighting intensity, surface subsidence rate, and microseismic data evolution before and after the working face entered the fractured zone. The results show that: Sufficient fracturing pressure can break the rock and cause continuous fractures in the rock mass. The surface vertical well fracturing process created artificial fractures of moderate scale and stable spatial distribution, effectively weakening the integrity of the thick and hard roof overlying the working face. After the working face entered the fractured zone, the roof weighting interval, weighting intensity, and weighting duration all decreased significantly. The surface subsidence rate increased markedly—2.67 times higher than before the working face entered the gob-side area and 2.18 times higher than when it entered the unfractured gob-side area—allowing the overburden subsidence deformation to develop fully in advance. In the fractured zone, the daily average and per-linear-meter microseismic energy increased somewhat, but no large energy events of 10⁴ J or above occurred. The roof break height decreased, and microseismic activity shifted away from the coal wall, achieving a pressure-relief effect characterized by weak impact, low energy levels, and decentralized breaking of the thick, hard roof. Surface vertical well fracturing can pre-fracture and weaken the thick, hard roof, disperse and release concentrated stress, reduce mine pressure manifestation, suppress high-level violent fracturing, and effectively lower the risk of mine tremors in rapidly advancing deep working faces with high mine pressure and thick, hard roof.