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The stress-relief coal mine methane surface gas venthole is considered an effective method by which to realize coal mine methane exploitation and outburst prevention. Existing stress permeability models for caved zones, fractured zones, and bending subsidence zones were embedded into FLAC3D simulation software by using the FISH language. In cooperation with the in-situ data of a mine in a Huainan coalfield, the permeability distribution of pressure-relief surface gas drainage via different zones was simulated. The results indicated that the surface gas ventholes were effective for gas extraction from mining areas. By analyzing the distribution of permeability, three zones were identified: (1) the fully compacted zone, (2) the gradually compacted zone, and (3) the “O” type fractured zone. The seepage path of pressure-relief surface gas drainage was visualized. Most of the gas seeps into the adjacent rock mass at first and then is extracted through surface gas ventholes. Meanwhile, seepage of gas with different ventilation modes in longwall-panel, U-type, and Y-type was analyzed. Results shows that the Y-type ventilation mode is better than the U-type for gob gas control in the longwall panel. A comparison between the simulated model and the on-site recorded data is conducted, and results show that the model represents the site condition reasonably well. The simulation results provide theoretical guidance to engineering practice.

Numerical Simulation of Surface Gas Venthole Extraction and the Effect of Ventilation Mode in Pressure-Relief Mining