Research on key technology of large diameter pressure relief drilling

Pressure relief by large-diameter Borehole in coal seam is a local method to solve the danger of rock burst. By means of pressure relief drilling in the coal body, So that the pressure relief areas around the drill holes are connected and connected with each other to form a weakening zone, thereby reducing the bearing capacity of the coal seam, redistributing the stress of the coal body under the action of high stress, and reducing the risk of impact of the coal and rock mass, in order to prevent the occurrence of rock burst. A large torque drilling equipment with a diameter of 300mm was developed. Through the field industrial test of Geng Cun Coal mine, through electromagnetic wave CT detection of the coal side of the borehole and comprehensive analysis of the test data, it was found that the proportion of coal and rock mass that can be weakened in the pressure relief zone composed of 300mm boreholes with spacing of 1m was 79.2%. In the pressure relief zone formed by 300mm boreholes with 0.6m spacing, 86.2% of the coal and rock mass can be weakened.