Research on Coal Body Water Injection Seepage Model and Main Control Fac-tors Based on CT 3D Reconstruction

Coal seam water injection technology is one of the main technical means of mine dust removal, which plays the role of wetting the coal source and reducing dust. However, with the increase of mining depth, the geological conditions become more and more complex, which greatly affects the wetting effect of coal seam water injection, and brings great challenges to the prediction of wetting range. Therefore, in order to improve the effect of coal seam water injection, combined with the intrinsic properties of coal and the scale of pores and fissures, firstly, the connected porosity was introduced, and the seepage model including pore throat, equivalent pore size, effective porosity, capillary bundle, tortuosity and flow path was established. The three-dimensional reconstruction of the coal with different metamorphic degrees in the five coal mines of Dahuangshan Coal Mine and Cijiaogou Coal Mine was carried out to visualize the microscopic effective pore fracture structure of the coal body, and the effec-tive connected pore fracture structure parameters of the three-dimensional reconstruction coal body were extract-ed by fractal theory for calculation. In order to characterize the influence of each influencing factor on the seepage flow, the Morris screening method was used to couple the numerical analysis method with the seepage model, and the main controlling factors such as the solidity coefficient, the fractal dimension of curvature, the effective po-rosity, the volume integral dimension, and the pore throat radius were quantitatively screened, and the influence of each controlling factor on the water injection capacity was analyzed. The following conclusions are drawn: 1) a seepage model including coal solidity coefficient, tortuosity fractal dimension, effective porosity, volume fractal dimension and pore throat radius is established, which can be used to measure the water injection capacity of coal in different areas such as Inner Mongolia, Tongfuxin Coal Mine, Meihuajing Coal Mine, Dahuangshan Coal Mine and Cijiaogou Coal Mine through calculation and comparison;2) The main controlling factors affecting the water injection capacity of coal seams are coal solidity coefficient, tortuosity fractal dimension, effective porosity, volume integral shape dimension, pore throat radius, in which the sensitivity of the coal solidity coefficient is the largest, reaching 16.765;3) The influence of the main controlling factors on the water injection capacity was comprehensively evaluated, and the relationship between the water injection capacity and the solidity coefficient (f) was distributed in a sinusoidal curve, and the water injection capacity increased with the increase of the effec-tive porosity, and the fractal dimension of curvature and volume fractional dimension decreased, and the stronger the water injection capacity. The research results can provide a theoretical basis for further improving the theory of coal seam water injection seepage, enhancing the wetting effect of coal seam water injection, and preventing and controlling mine dust.