Calculation Model of Gas Pre-drainage Radius by Boreholes and Analysis onIts Application Effect

Based on the basic assumptions, a calculation model of gas pre-drainage radius by boreholes in the coal seam was established, and the analytical solution of the model was analyzed and discussed. On the basis of the basic parameters of the original gas in M₉ coal seam of Anshun Coal Mine, the relation between the gas pre-drainage time and the pre-drainage radius of M₉ coal seam was calculated by using the derived formula. The K₁values of pre-drainage boreholes with different spacings in the original coal bady, 9102 and 9100 working faces of M₉coal seam were determined, and the rationality of the pre-drainage borehole spacing was comparatively analyzed. According to the the calculation and on-the-spot inspection data, the relation between the pre-drainage time and pre-drainage radius of M₉ coal seam was comprehensively determined.