Semipermeable Membrane Properties and Chemo-mechanical Coupling in Clay Barriers

In this chapter, the semipermeable behavior of clay-rocks is mainly exemplified on fluid flow. For such media and besidespressure gradients, other driving forces not accounted for in the classical form of Darcy's law describes fluid flow. In thecontext of coupled transport processes, the additional driving forces are chemical, electrical potential and thermalgradients. Consequently, the resulting so-called osmotic fluxes must be considered in clay media for hydrodynamic andtransport calculations. All available osmotic conductivity data have been collected here, including the most recent valuesacquired in the course of ongoing research on nuclear waste confinement in clay-rock formations. By means of adjustedcurves, these data can be directly used as abacuses. The data are also used to support some theoretical calculations, someof which are presented and discussed here. These predictive models (theoretical expressions or abacuses) for osmoticparameters make it possible to perform some fluid and transport calculations within clay-rock formations. Therefore, theycan be conveniently used for pore pressure profiles interpretation within clay stratigraphic layer, calculation ofcharacteristic times of solute migration through Peclet number characterization, or even steady or transient state directtransport calculations. For transient state hydrodynamics, the identification of the required chemomechanical couplingcoefficient is analyzed in the light of the most recent theoretical work