Diffusion in Unsaturated Swelling Clayey Materials

The experiment consist in mapping the swelling and the spatial distribution of the phases (air, water, intact clay and swelled clay) in partially saturated clayey materials. Osmotic technique is used to control the saturation of the sample. The 100 mm3 sample made of Benthonite powder is confined in an Al cell immersed in a controlled concentration PEG solution. The final objective is twofold. First determine the porosity changes triggers by the clay swelling and compare to the theoretical models and the macroscopic mechanical experiments (focusing on the anisotropy and spatial heterogeneity of the swelling process). Second, perform diffusion simulations on the segmented images in order to compare the results with a large set of laboratory experiments performed during the last 3 years, showing orders of magnitude lower diffusion coefficient values for the partially saturated cases compared to the saturated case, and postulated to be the result of multi-scalar air-water heterogeneities