Laboratory characterization of the chemo-hydro-mechanical behaviour of chemically sensitive clays

This paper focuses on the chemo-hydro-mechanical behaviour of active soils, with special reference to the effects of pore water salinity on the volumetric and shear strength behaviour. Fundamental coupled processes governing transport of solvent and solute in active materials are briefly recalled, together with a model for the volumetric behaviour at the macroscopic scale based on the evaluation of the electrical interaction between clay particles and ions in the pore water at the particle level. Experimental procedures for the laboratory characterization of active soils are then discussed in light of these models and of other well-known phenomenological evidences. Both modified and conventional experimental apparatus can be used in the geotechnical characterization: interpretation of test results requires anyway referring to models accounting for the chemo-mechanical coupling. Experimental data discussed in the paper proceed from tests on bentonites used for waste containment and from tests on a natural illitic-smectitic soil from a marly clay formation in the Langhe area.