含瓦斯煤Forchheimer型非达西渗流实验研究

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

针对目前非达西渗流在含瓦斯煤三轴应力状态下研究较少的问题,基于Forchheimer型非达西渗流理论,采用自行研制的含瓦斯煤准三轴渗流试验装置,研究了2个煤矿的贫煤煤样在不同围压、轴压条件下Forchheimer型非达西渗流特性并计算了相关参数。研究结果表明,三轴应力状态下煤样中瓦斯气体流速随瓦斯压力梯度的变化而出现明显的Forchheimer型效应。相同介质和流体下,瓦斯压力和三轴应力状态成为煤体瓦斯渗透规律的主要影响因素。不同围压、轴压条件下,瓦斯渗透速度会随瓦斯压力的增大而增大,但其渗透速度的增大速率最终会趋于恒定。相同围压下,非达西渗流因子β随轴压的增大而增大,且β越大,压力梯度与渗流速度之间的非线性关系越明显,而非达西渗透系数K值会有减小的趋势。

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 factorβ i s ’ the more obvious the nonlinear relationship between the pressure gradient and gas flow velocity i s’ while the Forchheimer’s non-Darcy permeability coefficient K value will decrease.