利用动电模型分析黏土渗流的耦合动力学性状

从水头?诱导电位耦合驱动的角度，探讨分析黏土?水溶液体系的流体动力学性状。为此，借助动电输运原理，耦合Poisson-Boltzmann、Nernst-Planck、Navier-Stokes方程，建立了“广义力”驱动“广义流”的耦合关系。模型从黏土代表性单元体入手，计算确定各项耦合系数，用以定量考察离子迁移、流体运动的耦合性状。计算表明：采用Debye-Huckel近似计算黏土双电层电位将引起显著的误差；诱导电位产生的原因在于维持体系的电中性，其梯度大小正比于正负离子间因水头迁移性的差异而产生的潜在分离程度；诱导电位作用于离子迁移的方式在于阻滞正离子迁移，助推负离子迁移，而作用于流体运动的方式在于引起反向电渗，进而削弱水头驱动下的正向渗流；高表面带电密度的黏土矿物（如蒙脱土）处于低孔隙率的状态时，诱导电位对于渗流的削弱程度有可能异常显著。因此，建议相应的水头渗透系数的测定需要充分考虑诱导电位的影响，否则将导致较为显著的误差。

Analysis of flow in clay using electrokinetics considering coupling driving forces

This paper attempts an in-depth analysis on the hydrodynamic behavior of clays considering the multiple driving forces of pressure and induced electrical potential (IEP). Electrokinetics is employed to quantify the processes of ion migration, fluid motion, and potential distribution, which are described by the coupled equations of the Nernst-Planck (NP), the Navier-Stokes (NS), and the Poisson-Boltzmann (PB), respectively. The numerical investigation shows that employment of Debye-Huckel approximation may be inappropriate for clays in calculation of double layer potential since their relatively high surface charge density. IEP is caused by the requirement of electroneutrality for the clay-water system, and is directly proportional to the separation of cation-anion resulting from the differential hydraulic migratability between them. IEP contributes to decelerating cation, accelerating anion, and producing a negative electroosmosis that counteracts in partial the positive flow driven by pressure. At those conditions including low concentration, small porosity, and high surface charge density, double layer effects may be enhanced, leading to significant effects both in IEP and its flow reduction.