EXPERIMENTAL EVIDENCE OF THE INTERACTION BETWEEN THM BEHAVIOUR AND GEOCHEMISTRY IN BENTONITES

摘要

This paper presents results from different experimental studies of the effect of changes in pore water composition on the hydro-mechanical properties (swelling, permeability and water retention) of two buffer materials, namely the MX-80 and FEBEX bentonites. Swelling tests have shown that the swelling capacity of the FEBEX bentonite reduces as the salinity of the solution increases, with osmotic consolidation even observed if salinity is very high. These chemically induced strains are largely reversible. In the bentonites tested, permeability increased slightly with the salinity of the permeant. Salinity increases the retention capacity of the bentonite, the osmotic suction of the natural bentonite being low with respect to the matric suction. The experimental results available indicate that the effect of salinity on HM properties is lower when the density or stress state of the material is high and depends on the predominant cation in the solution.