Research on reasonable sealing depth and grouting parameters of bedding gas drainage drilling

In order to improve the sealing performance of bedding gas drainage drilling, reasonable sealing depth and grouting parameter are studied based on the geological conditions of No.8 coal seam in Wulunshan Coal Mine in Guizhou.By analyzing the influencing factors of drilling air leakage, the air leakage can be divided into four types:the air leakage in the fracture zone of the roadway, the air leakage in the fracture zone of the drilling, the air leakage at the edge of the drilling wall, and the air leakage of the materials in the sealing section. Theoretical analysis, numerical simulation and field test were used to study the stress distribution law around the roadway and drilling, and the reasonable drilling sealing depth was determined to be 15 m, and the reasonable grouting diffusion radius was from 0.40 m to 0.50 m. A new type of sealing material was developed, with the compressive strength increased by 20 MPa, the expansion rate increased by 20%, the viscosity decreased by 23%, and the final setting time reduced by 5 h. Based on the diffusion theory of grouting cylinder, the reasonable grouting pressure was determined to be 1.5 MPa, and the reasonable grouting amount was determined to 0.3 m³.In 1811 working face, 16 bedding gas extraction drillings were arranged in transport roadway, and 4 groups of industrial tests were carried out under different sealing parameters. The results show that the sealing performance and economy is good when the sealing depth is 15 m, the grouting pressure is 1.5 MPa and the grouting volume is 0.3 m³, and the average gas concentration of drilling is increased by 30%.