3D numerical simulation of gas drainage from boreholes based on solid-gas coupling model of coal containing gas.

An effective stress calculation formula was proposed for coal containing gas with considering the swelling stress of gas adsorption based on the effective stress principles for porous media. Referring to dynamic model of porosity and permeability in coal containing gas, solid-gas coupling model which could describe the skeleton deformability of coal containing gas and the compressibility of gas under the solid-gas interaction condition was built. First we made excavation on the three-dimensional model based on the physical parameters of Pingdingshan tenth coal mine to obtain the stress distribution of coal seam after excavated instead of easy uniform loading. Then we simulated the gas drainage from boreholes based on constructed mathematical model. From the results we got: (1) Negative pressure didn't have a great influence on gas drainage. (2) The porosity of coal seam decreased gradually over time. (3) The effective radius increased gradually to a fixed value over time. [ABSTRACT FROM AUTHOR]