Modelling Hydro-Chemo-Mechanical Behaviour of Active Clays Through the Fabric Boundary Surface

The osmotic, hydraulic and self-healing efficiency of bentonite based barriers (e.g. geosynthetic clay liners) for containment of polluting solutes are governed both by the physico-chemical intrinsic parameters of the bentonite, i.e. the solid density, the total specific surface, and the total fixed negative electric surface charge, and by the state and fabric parameters able to quantify the soil density and microstructure, i.e. the total and nano void ratio, the average number of platelets per tactoid, the effective electric fixed-charge concentration, and the Stern fraction. In turn, the fabric parameters seem to be controlled by the effective stress history, ionic valence and related exposure sequence of salt concentrations in the pore solution. A theoretical framework able to describe chemical, hydraulic and mechanical behaviours of bentonites has been set up. In particular, the relationships, linking the aforementioned intrinsic, state and fabric parameters of a given bentonite with its hydraulic conductivity, effective diffusion coefficient, osmotic coefficient and swelling pressure under different stress histories and solute concentration sequences, are presented. The proposed theoretical framework has been validated by comparison of its predictions with some of the available experimental results on bentonites.