多孔介质曲折度对膨润土衬垫渗透性能的影响

膨润土的颗粒膨胀所引起的孔隙率及流径曲折度的改变是影响膨润土衬垫(Geo?synthetic Clay Liner,GCL)防渗性能的关键.通过COMSOL建立模拟膨润土中渗流的数值模型,研究了膨润土颗粒膨胀过程对GCL防渗性能的影响.COMSOL模型研究结果表明,流体通过膨润土粒间孔隙时,边界通道的最大速度明显小于非边界通道速度,这与泊肃叶公式的基本结论一致,初步验证了模型的准确性.同时,微观粒子速度分布规律与宏观流体场的速度分布规律基本一致,因此可以从微观的角度研究GCL的宏观渗透规律.利用COMSOL中的粒子轨迹监测方法,分析了颗粒膨胀对膨润土孔隙率和流径曲折度的影响.研究结果表明,流径的曲折度随孔隙率的增加而减小,且呈指数函数关系.基于GCL试样的多孔介质毛管模型和修正泊肃叶公式,考虑GCL孔隙率与流径曲折度之间的指数函数关系,提出了能综合反映孔隙率与流径曲折度影响的GCL渗透系数理论预测模型,并将理论预测结果与已有文献试验数据进行了对比,两者的比值介于1/5～5,验证了模型的准确性.

Influence of Porosity and Tortuosity on HydraulicConductive of Geosynthetic Clay Liner

The change of porosity and the tortuosity induced by the swelling progress of Geosynthetic Clay Liner(GCL) influence the hydraulic conductive obviously. The model simulating the seepage in bentonite is established byCOMSOL to investigate the effect of the expansion process of bentonite particles on the hydraulic conductive of GCL.The COMSOL simulation results showed that the maximum velocity of the boundary channel is less than that of thenon-boundary channel, when the liquid passes through the pores between the bentonite particles, which is consistentwith the Poiseuille equation and initially verifies the accuracy of the model. The microscopic particle velocity distri?bution law is consistent with the velocity distribution law of macroscopic fluid field. Therefore, the macroscopic hy?draulic law can be investigated in the microscopic aspect. Meanwhile, the particle expansion on the porosity and thetortuosity of bentonite is analyzed by using the particle trajectory monitoring method in COMSOL. The results showedthat the tortuosity decreases with the increase of porosity, and it is exponentially functional. Based on the capillarymodel of porous media and the Poiseuille Formula, the theoretical prediction model of the hydraulic conductive ofGCL, which can reflect the influence of porosity and the tortuosity, is proposed, considering the exponential functionrelationship between the porosity and the tortuosity. The theoretical calculation prediction model for predicting thehydraulic conductive of GCL is proposed. The ratio of the theoretical and experiments is between 1/5 and 5, whichconfirms the accuracy of the theoretical model of GCL.