Effect of a partial saturation on the hydromechanical response of a clay rock

Abstract

The behaviour of claystones and shales ispresently investigated in details in link withtheir potential use as host rock for radioactive waste disposal at great depth. Claystones are verysensitive to changes in water content, with an increase of their mechanical properties withdesaturation under increased suction. Claystones have standard water retention properties butsome effect of hydric damage is observed after a drying-wetting cycle that results in enhancedswelling. The microstructure of the Callovo-Oxfordian claystone tested here is characterized by aclay matrix (50% clay fraction) made up of clay platelets that can be assimilated to bricks. The poresize distribution is well organized around a mean diameter of 32nm that provides an idea of themean thickness of the platelets. A stress release at constant water content results in a swelling anddesaturation due to an internal transfer from free inter-platelets water to linked intra-plateletswater.