颗粒堆积型多孔介质非线性渗流的试验研究

Experimental Research on Nonlinear Seepage of Porous Media of Pellets Packing

采用SLB-1型应力应变式三轴剪切渗透试验仪对颗粒型多孔介质试样进行了恒围压与恒轴压不同孔隙压力条件下的渗流试验,考虑到颗粒型多孔介质渗透系数依赖于孔隙改变的特点,提出渗透系数的非线性数学模型。研究结果表明,渗流过程分为非稳定与稳定渗流两个阶段;渗透系数随着轴压和围压的减小由非线性逐渐趋于线性;一维稳定渗流问题的理论推导表明试样内部孔隙压力梯度具有非均匀性。结合试验数据,采用最小二乘法确定了渗透系数理论模型的待定参数,利用非线性数学模型与Darcy定律计算得到的渗透系数之比约为2.5倍。

Permeable experiments on porous media of pellets packing under the condition of constant confining pressure, constant axial pressure and different pore pressure were carried out in a type SLB-1 triaxial compression apparatus. In consideration of the character that permeability of poroelastic media varies with its deformation, a nonlinear mathematical model of per- meability coefficient is established. The research result shows that the seepage process consists of unstable and stable seepage stages. The permeability coefficient takes on the nonlinear characteristic, gradually close to linear with the decrease of the axial pressure and confining pressure. The thory deduce of one dimensional steady seepage problem illustrates that gradient of pore pressure in the testing sample is non-homogeneous. On the basis of the experimental data, parameters of theory model of permeability coefficient are determined by using least-squares. The permeability coefficient calculated by the nonlinear mathematical model is around 2.5 times as that by the Darcy law.