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

Area of Science:

• Mining Engineering
• Geotechnical Engineering
• Environmental Science

Background:

• Deep mining faces increasing severe gas hazards, challenging protected seam mining.
• Traditional methods struggle with effective gas management in these environments.

Purpose of the Study:

• To investigate the spatiotemporal effectiveness of pressure unloading from a distant stratum combined with gas extraction.
• To determine optimal conditions for gas drainage in protected coal seams (PCS).

Main Methods:

• Utilized Flac3D to analyze stress and displacement evolution in the PCS.
• Verified findings through measurements of coal seam deformation and unloading boundary investigation.
• Identified the optimal temporal window for gas drainage.

Main Results:

• Identified an optimal gas drainage window between 58 to 67 days for working face distances of 350-400 m.
• Observed a diminution coefficient of 0.62 and an expansive deformation rate of 5.83%.
• Achieved a cumulative gas extraction of 320,300 m³ with 34.3% efficiency, leaving residual gas volume of 3.68 m³/t at 0.5 MPa.

Conclusions:

• Pressure unloading from a distant stratum significantly enhances gas extraction effectiveness.
• Continuous gas extraction is achieved when transverse cracks in the PCS reach optimal pressure relief.
• The study provides a viable strategy for mitigating gas hazards in deep protected seam mining.