Research on the Prevention and Control of Blast Impact Pressure in Deep Holes and the Mechanism of Coordinated Extraction of Harmful Gases.

Uncontrolled carbon monoxide (CO) release after deep-hole roof pressure-relief blasting remains a safety problem because conventional shallow drainage often fails to match the strata where blast gases are generated and retained. Here, we clarify the permeability-contrast-controlled retention mechanism and propose an integrated blasting-sealing-extraction framework that couples field diagnosis at the A503 working face, dynamic fracture modeling, confined explosion tests, adsorption-diffusion analysis, and industrial validation. The method uses the critical distance between the fracture front and the coal seam to constrain charge length and places extraction boreholes in the roof gas-enrichment zone rather than only in the coal seam. The A503 measurements showed that the sandstone roof permeability (2.1 × 10-13 m2) was about 41 times lower than that of the coal seam (8.7 × 10-12 m2), creating a low-permeability CO retention zone. Numerical simulations gave an effective blasting influence radius of approximately 6.5 m and showed that the control hole extended the connected plastic zone to about 10 m. Field mass-balance data showed that the optimized scheme increased the CO extraction rate from 4.43% to 82.21%, reduced ventilation discharge from 11.96% to 3.91%, and lowered the residual CO fraction from 83.61% to approximately 13.9%. These results show that the mechanism-guided matching of fracture control, sealing, and targeted roof-strata extraction converts postblasting CO control from delayed ventilation dilution to active capture at the enrichment zone.