Semipermeable Membrane Properties and Chemo-mechanical Coupling in Clay Barriers
Résumé
In this chapter, the semipermeable behavior of clay-rocks is mainly exemplified on fluid flow. For such media and besides
pressure gradients, other driving forces not accounted for in the classical form of Darcy's law describes fluid flow. In the
context of coupled transport processes, the additional driving forces are chemical, electrical potential and thermal
gradients. Consequently, the resulting so-called osmotic fluxes must be considered in clay media for hydrodynamic and
transport calculations. All available osmotic conductivity data have been collected here, including the most recent values
acquired in the course of ongoing research on nuclear waste confinement in clay-rock formations. By means of adjusted
curves, these data can be directly used as abacuses. The data are also used to support some theoretical calculations, some
of which are presented and discussed here. These predictive models (theoretical expressions or abacuses) for osmotic
parameters make it possible to perform some fluid and transport calculations within clay-rock formations. Therefore, they
can be conveniently used for pore pressure profiles interpretation within clay stratigraphic layer, calculation of
characteristic times of solute migration through Peclet number characterization, or even steady or transient state direct
transport calculations. For transient state hydrodynamics, the identification of the required chemomechanical coupling
coefficient is analyzed in the light of the most recent theoretical work.