Experimental Study of Forchheimer’s Non-Darcy Seepage of Gas-containing Coal

Aiming at the less research on non－Darcy seepage of gas－containing coal under triaxial stress state and based on the Forchheimer’s non－Darcy seepage theory，study was carried out in this paper on the seepage characteristics of the meagre coal samples taken from two coal mines under the conditions of different confining and axial pressures with the self－developed triaxial seepage device and the calculation was made on relevant parameters of the Forchheimer’s non－Darcy seepage．The results showed that the gas flow velocity in the coal sample under the triaxial stress state presented an obvious Forchheimer’s effect with the change of gas pressure gradient．For the same medium and fluid，the gas pressure and the triaxial stress state are the main factors affecting the gas permeability in coal samples．Under the conditions of different confining and axial pressures，the gas permeation rate will increase with the increase of gas pressure，but it will finally become constant．Under the conditions of the same confining pressure，the Forchheimer’s non－Darcy seepage factor β will become greater with the increase of the axial pressure，and the greater the Forchheimer’s non－Darcy seepage factor β is，the more obvious the nonlinear relationship between the pressure gradient and gas flow velocity is，while the Forchheimer’s non－Darcy permeability coefficient K value will decrease．