Effectiveness Spatiotemporal of Pressure Unloading and Gas Extraction in Remote Upper Protected Seam Mining.

Severe gas hazards are increasing in deep mining areas, and there exists an enormous traditional challenge for protected seam mining. In this work, we conducted a multifaceted investigation into the spatiotemporal effectiveness exerted by pressure unloading from a distant safeguarded stratum in concert with the application of gas extraction methodologies. The stress and displacement evolution in the protected coal seam (PCS) are analyzed by applying Flac3D, and then positives are verified by the measurement of coal seam deformation and investigation of the unloading boundary. The results show that diminution coefficient of 0.62, and record an expansive deformation rate of 5.83%. The opportune temporal window for effective gas drainage is discerned, with its time window spans from 58 to 67 days as the expanse between 350 and 400 m progresses at the working face. Continuous and effective gas extraction occurs when transverse cracks in the PCS reach an optimal state of pressure relief. The final cumulative gas extraction was 320,300 m with an extraction efficiency of 34.3%. A residual gas volume of 3.68 m/t and a residual gas pressure of 0.5 MPa reflect the efficient gas extraction.