ABSTRACT

The factors affecting membrane behavior in bentonite specimens are illustrated with the aid of published data. A reduction in the void ratio of the soil due to an increase in stress is shown to result in an increase in membrane behavior as reflected by an increase in measured chemico-osmotic efficiency coefficients, ω, due to a decrease in the total volume of voids available to conduct solute migration. For a given void ratio representing a given state of stress, membrane behavior is shown to increase with a decrease in electrolyte concentration and a decrease in cation valence (charge) in accordance with the diffuse double layer (DDL) theory. Finally, membrane behavior is shown to result in two coupling effects with respect to solute diffusion, an explicit or theoretical “salt sieving” effect, and an empirical or implicit coupling effect. Preliminary results indicate that the implicit (empirical) coupling effect is more significant than the explicit (theoretical) coupling effect.