Research on the Pressure Relief Mechanism of Gently Inclined Long-Distance Lower Protective Layer Mining and Cooperative Gas Control Technology

This study investigates pressure relief mechanisms and gas migration control in gently inclined remote lower protective layer mining, using the Wu8-31220 working face of Pingdingshan Tianan Coal Industry’s No. 1 Mine as a prototype. The integrated approach combining theoretical modeling with multidimensional monitoring systems yielded critical insights into pressure relief patterns. Analysis demonstrated dip-oriented pressure relief angles measuring 77° (intake side) and 83° (return side), collectively establishing a pressure relief zone spanning 160.5 m. Concurrently, horizontal pressure relief angles were determined to be 60° in both orientations, generating a pressure relief zone extending 1261 m. Mechanical monitoring revealed multistage “compression–expansion” responses in the Ding6 seam during protective seam extraction, achieving maximum expansion deformations of 9.89–13.55‰ within the boundary zone. By optimizing borehole spacing (20 m) and extraction duration (8 months), the Ding6-32070 working face extracted 1.18 million m3 of gas (31.22% reserves), resolving spatial coupling challenges between gas recovery efficiency and pressure relief dimensions. This work advances understanding of pressure relief and permeability enhancement in gently inclined remote lower protective layer mining. The findings provide both theoretical foundations and technical benchmarks for safe deep coal mining operations and efficient gas control strategies.