Coupling analysis of macroscopic and microscopic behaviour in highly consolidated Na-laponite clays

The great importance of problems related to the storage of chemical and radioactive wastes requires better understanding of the behaviour of the host media. In the case of clay soils, their behaviour is controlled by their microtexture, their mineral composition and their physico-chemical properties (interaction between interstitial fluid and solid matrix). In this paper, the analysis of the behaviour of consolidated synthetic model clay Na-laponite is presented. Tests are conducted on samples submitted to axial stress for the determination of the distribution of pore space and the type of interstitial water. Analysis is based on data given by different techniques: BET, mercury intrusion, X-ray diffraction and thermogravimetric analysis. The basal spacing d(001) and the water content decrease respectively from 2.5 nm to 1.6 nm and from 140% to 63% when the axial mechanical stress increases from 1 to 10 MPa. Results obtained would allow to take into account the relationships between the applied stress on the samples and the basal spacing, the number of water layers and the water content in the formulation of numerical modelling of the macroscopic behaviour.