Deformation and permeability model of coal and rock considering moisture content

The depth of coal mining is increasing,and the increase of gas content in coal seams leads to the gradual in- crease of dynamic disasters,which brings severe challenges to the safe production of coal mines. Research on the flow of gas in coal seams has always been a concern and the permeability is one of the key parameters affecting gas flow in coal seams. With the application of the coal containing gas heat-fluid-solid coupling device of three axis servo seepage, it can simulate the deformation and seepage characteristics of coal mining caused by the environment through the ex- perimental studies on the permeability of the process of the coal when the pore pressure are under different saturated conditions. Then considering moisture content,the authors establishes an adsorption equation and adsorption-permea- bility model so as to model the common effect of water content and pore pressure on the deformation and permeability characteristics of coal. The results show that:① in the process of pore pressure increase,the radial strain and axial strain decrease with the pore pressure increases,and the change of gas flow increases. Due to gas adsorption,coal ma- trix swells,and the volumetric strain decreases gradually. ② When the water content is constant,and with the increase of pore pressure,the gas adsorption capacity increases first and then levels off. The coal gas adsorption capacity and deformation decrease with the increase in moisture content when the pore pressure is constant. ③ Under constant mois- ture conditions,coal permeability curve decreases first and then levels off with the pore pressure increase. Under a con- stant pore pressure,with the increase of moisture content of coal,the permeability decreases gradually,the higher mois- ture content of pore pressure,the less effect on the permeability by pore pressure,the stronger effect on permeability by water molecules. ④ The calculation formula of the adsorption amount considering the water content is constructed,and on this basis,the coal adsorption-permeability model considering the water content is further constructed. The calculat- ed permeability value is basically consistent with the experimental results,which reflects the variation law of coal per- meability.