Experimental study of the thermo-hydro-mechanical behaviour of indurated clays

Indurated clays are being considered in a number of counties as a host rock for disposal of radioactive waste. This paper describes laboratory experiments carried out at the GRS geotechnical laboratory in Braunschweig on core samples taken from the Callovo-Oxfordian argillite at Bure in France and the Opalinus clay at Mont Terri in Switzerland. The experiments focused on investigating responses of the clay rocks to thermo-hydro-mechanical (THM) loading similar to that expected in repositories. Very complex coupled THM phenomena were observed in the tests, such as significant swelling and shrinking induced by wetting and drying, stress reaction to hydration and dehydration, pore-water pressure increase, thermal expansion and contraction, thermal effects on deformation and strength, and self-sealing. All the laboratory observations suggest that adsorbed pore-water is a key factor dominating the THM properties and processes in indurated clays.