| Gas disasters threat to the safe and efficient production of mine seriously.Simultaneously, gas is a clean energy with high calorific value. The multiphysics coupling research of gas migration is the basis of preventing gas dynamic disasters and making use of gas drainage. Permeability of coal seam containing gas is an important physical parameter of multiphysics coupling of gas migration. Moreover, it reflects the degree of difficulty of gas seepage in coal seam.In this paper, gas seepage experimental system with three axes were used in State Key Laboratory Cultivation Base for Gas Geology and Gas control and raw coal was taken as the object. The experimental on seepage characteristics of coal seam containing gas was studied under different conditions of stress and gas pressure. The model of multiphysics coupling of gas migration was established considering adsorption effect and dynamic changes of permeability. Then the established model was applied to the engineering practice of gas extraction effective radius and numerical simulation analysis was carried out with the help of COMSOL numerical software. The conclusions were obtained as follows.(1) The trend of coal seam containing gas permeability presents an obvious periodic characteristic under the influence of different porosity gas pressure. The permeability decreased first and then increased gradually with the increasing of gas.(2)The permeability of coal seam containing gas decreased gradually with the increase of confining pressure. Furthermore, the tendency of decrease was becoming more and more gentle. So the relationship between confining pressure and permeability of coal seam containing gas was a negative exponential function.( 3) The impact of gas pressure and confining pressure as well as axial compression on percolation characteristics of coal seam containing gas is different.The change of permeability is controlled by porosity evolution generated by coal load deformation in various stages of stress and strain.(4)In the process of gas extraction, coal seam gas pressure show a downward trend and the overall rate of decline reduced gradually with the increase of extraction time. L9(34) orthogonal table was selected to carry out the orthogonal experimentabout the factors of gas drainage effective radius. The degree of the four main factors chosen for gas drainage effective radius were as follows: the initial permeability, the original gas pressure, extraction time and drilling aperture. With the analysis of variance, the initial permeability took the most significant impact on Effective drainage radius and drilling aperture was the least significant.(5)The gas drainage effective radius for 30 days in expand district No. 2 seam of Shen Family Mine was measured between 2m and 3m. The measured results agreed with the simulation results, which verified the correctness of the multiphysics coupling model. |
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