Research on Hydraulic Fracturing Pressure Relief and Improvement Permeability Technology of the Soft Coal Seam Roof.

Aiming at the characteristics of low permeability and large gas content of deep soft coal seam, hydraulic fracturing pressure relief and improvement permeability technology of the roof are proposed. FLAC3D was used to invert the roof hydraulic fracturing of the soft coal seams. On this basis, the dynamic evolution characteristics of permeability before and after fracturing were given by the COMSOL multiphysics software. Finally, roof hydraulic fracturing technology was applied on the site. The results show that after the hydraulic fracture of the roof, the peak stress on both sides of the roadway is reduced by 1.7 MPa, the peak stress concentration in front of the roadway is reduced by 2.2 MPa, the stress concentration range is reduced, and the stress is effectively transferred to the deep part of the roadway. After fracturing, the permeability of the stress concentration area increased by 2.18 times, the permeability of the original rock stress area increased by 1.84 times, and the gas fluidity improved. After roof hydraulic fracturing, the occurrence of a coal cannon decreases from 2 to 4 times per 1 m driving to 0 to 1 times, and the phenomenon of a coal cannon at the working face decreases significantly. The concentration of the return air flow is reduced from 0.5-0.9% to 0.2-0.4%. The results of this study have a guiding role in taking the corresponding measures for gas disaster prevention and control.