Electro-chemo-mechanical couplings in swelling clays derived from a micro/macro-homogenization procedure

A macroscopic model for highly compacted expansive clays composed of a charged solid phase saturated by a binary monovalent aqueous electrolyte solution is derived based on a rigorous scale-up of the microstructural behavior. The homogenization technique is applied to propagate information available in the pore-scale model to the macroscale. Macroscopic electrokinetic phenomena such as electro-osmotic flow driven by streaming potential gradients, electrophoretic motion of mobile charges and osmotically induced swelling are derived by homogenizing the microscopic electro-hydrodynamics coupled with the Nernst–Planck and Poisson–Boltzmann equations governing the flow of the electrolyte solution, ion movement and electric potential distribution. A notable consequence of the upscaling procedure proposed herein are the micromechanical representations for the electrokinetic coefficients and swelling pressure. The two-scale model is discretized by the finite element method and applied to numerically simulate contaminant migration and electrokinetic attenuation through a compacted clay liner underneath a sanitary landfill