Transient Analysis of Ionic Replacements in Elastic-plastic Expansive Clays

Chemically active saturated clays are considered in a two-phase framework. The solid phase contains clay particles,absorbed water and dissolved ions, Naþ, Kþ and Cl_. The fluid phase, or pore water, contains free water and the same ionic species. Water and ions can transfer between the two phases. In addition, they diffuse through the porous medium.A global understanding of all phenomena, mass transfer, diffusion/advection and deformation is provided. The coupled constitutive equations associated to these phenomena are developed. Emphasis is laid on the electro-chemo-mechanical constitutive equations in an elastic–plastic setting. A finite element formulation embodying all the above aspects is proposed and simulations of oedometer tests are presented and commented. Of particular interest are the consolidation and swelling that occur during salinization and desalinization of an external reservoir in contact with the specimen, and the more subtle, but important effects of replacing an NaCl pore solution by a KCl pore solution, and conversely.