A model for the volume change behavior of heavily compacted swelling clays

Engineered clay barriers used for isolating nuclear waste disposal at great depth are made of dense compacted swelling clays. Hydration tests carried out on the French FoCa7 clay showed some limitations of existing elastoplastic models for swelling soils, which are developed for looser swelling soils [Canadian Geotechnical Journal 29 (1992) 1013]. In dense compacted swelling clays, wetting–drying and loading–unloading tests showed a reversible volume change behavior, related to the absence of collapsible macropores. Based on experimental results, an elastic non-linear model is developed. The concept of critical swelling curve (CSC) is introduced, and constitutes the base of the model. This CSC curve and the model developed account for the couplings existing between hydraulic and mechanical effects, and provide satisfactory predictions of the volume change behavior of heavily compacted swelling clays.