Research On Fuid-Solid Coupling Model Of Loaded Coal Containing Gas And Its Application

Coal is a medium with complicated physical and mechanical properties. Gas flow in the coal is the gas migration under the function of fluid-solid coupling, which is also caused the emergence of instable failure of gaseous coal-- coal and gas outburst. So it is necessary to study on the coupling function of coal deformation and gas flow, explore the coupling law and analyze the stability of structure and motion in the gaseous coal.The above researches on the coupling function and its law are of great theoretical and practical engineering importance to further examine the outburst mechanism of loaded gaseous coal and mechanism of gas drainage, and adopt some safety procedures accordingly. Meanwhile, seepage(which is the index showing how difficult gas flows in the coal) and the fluid-solid coupling model together play the fundamental and most important role in the study on the law of gas flow in the loaded coal containing gas.Therefore, based on seepage mechanism, elastic-plastic theory, fluid dynamics and fuzzy mathematics and so on, the systematic researches on the law of gas flow are made by taking the coal samples of the typical coal mine as the research object, and by the use of experiment platform of gaseous coal fluid-solid coupling and seepage & the coal gas outburst simulation experiment system; then the major results have been obtained as follows:1) The influencing rules of gas seepage of the original coal samples are obtained by analyzing and regressively analyzing the coal seepage under the different influencing factors, namely effective stress, gas pressure, confining pressure and moisture content,with the self-developed experiment platform of gaseous coal multi- coupling at the constant temperature. The fitting equation of each influencing factor and seepage is established by use of the mathematical least squares principle; the notion of coupling factor is introduced and the method to determine it is also proposed according to the fuzzy complementary judgment matrix. Then the comprehensive equation of seepage and effective stress is established under different moisture content, and applied to modify the seepage k in the control equation of gas migration.2) The pore structure of coal containing gas and fissure structure characteristics of porosity fracture are analyzed on the basis of scanning the coal samples of the typicalcoal mine with tungsten filament of electron microscope. According to basic definition of force balance principle and the porosity, dynamic evolution equation for porosity of coal containing gas is proposed with considering the adsorption deformation and pore gas compression volume; and hence the total stress expression equation of the gaseous coal is derived based on the above research results on the porosity especially the absorption and expansion stressp?, and pore pressure to the compression stress of coal and rock skeletonf?.3) The fluid-solid constitutive relation of coal containing gas is revised considered coal deformation compressed coal and rock skeleton gas adsorption swelling strain, the free gas strain and the strain of the external load function; and based on the equilibrium differential equation, geometric equation and physical equation, the displacement deformation field equation of coal containing gas is also established taken adsorption swelling stress and pore gas pressure into account; combined with the derived gas migration simultaneous inference control equation and deformation field equation of gassy coal, the fluid-solid coupling model of the loaded gaseous coal is established with gas pressure and effective stress for the transfer control parameter; furthermore, the boundary condition of stress field and seepage field of the model is given.4) With self-developed coal gas outburst simulation experiment system, the physical simulation experiments are conducted on the gas flow of loaded coal containing gas, meanwhile, the rules of the changes in gas pressure and effective stress are monitored; the fluid-solid coupling model is fitted into the numerical computation model, which is established on the background of the former physical simulation experiments, and then worked out the rules of the changes in gas pressure and effective stress in the monitoring points by the use of COMSOL-Multiphysic; the correctness of the fluid-solid coupling model is also verified by comparing and analyzing the results of physical experiments and numerical computation.5) The three-dimensional numerical computation model is established to solve the engineering problems that there are stress concentration and the transfinite gas checking index after the implementation of hydraulic flushing borehole to prevent gas outburst in22011 working face of a coal mine of Henan energy chemical group. And then the fluid-solid coupling model of gaseous coal is embedded into the three-dimensionalnumerical computation model to calculate the quantitative relationship between the effective influence radius of the hydraulic flushing and the coal amount, which can be applied in the optimization of assigning hydraulic flushing and drills. It can be seen by actual verification that the design of hydraulic flushing and drills has solved the problems of leaving blank and the transfinite gas checking index after the implementation of hydraulic flushing borehole through site inspection, The good field test effects of the simulation results also verify the rationality of the derived theoretical models.