Numerical simulation research on effective influence radius of hydraulic punching in inclined coal seam

Current research on hydraulic punching technology seldom considers that pressure relief range of hydraulic punching in inclined coal seam varies with direction and influence of coal seam inclination on the effective radius of hydraulic punching pressure relief. In view of the above problem,taking the coal seam No.3 of a coal mine as research object, the effective influence radius for inclined coal seam under hydraulic punching was numerically simulated by using multi-physics coupling numerical simulation software COMSOL Multiphysics. The effective extraction radius of borehole in different directions was studied. The numerical simulation results show that under the action of punching, the range of extraction influences continues to increase with the increase of extraction time, but the expansion speed decreases with time. Due to the stress relief under punching, the permeability of coal seam is greatly increased, and the influence range around the borehole is approximately elliptic. After 90 days of continuous extraction, the influence radius is about 6 m in the upper direction, the influence radius is about 4 m in the lower direction and the influence radius is about 5 m in the horizontal direction. In order to reach the gas extraction standard, the horizontal drilling arrangement spacing of the hydraulic drilling tunnel of the coal seam is about 3.5 m, and the longitudinal drilling arrangement spacing is about 4.0 m. The research results have important practical significance for optimizing hydraulic punching process parameters, guiding the accurate layout of extraction boreholes, and enhancing the gas control effect of the mine.