Influence of dry density and water content on the swelling of a compacted bentonite

In the context of a project for the study of the behaviour of the clay barrier in a nuclear waste repository, the swelling properties of compacted bentonite have been investigated. Results on the influence of initial dry density and water content on the swelling pressure and swelling deformation of a compacted bentonite are presented. Swelling pressure is exponentially related to dry density but is rather independent of the initial water content of the clay. The swelling capacity is mainly affected by the vertical load under which saturation takes place. It increases with initial dry density but decreases as the initial water content is higher. The effect of the initial water content on the final swelling strain is less important for the low dry densities and the high vertical loads, becoming negligible for vertical loads close to the swelling pressure. These features of behaviour agree with the predictions of conceptual models that consider the interaction between the responses of the microstructure and the macrostructure of the material to suction and stress changes.