Moisture effects on argillaceous rocks

In view of the disposal of high level radioactive waste in argillaceous rocks various laboratory experiments have been performed at GRS's geotechnical laboratory oil samples drilled from the Opalinus clay at the Mont Terri Rock Laboratory in Switzerland and the Callovo-Oxfordian, argillite at the Bure site in France. This paper focuses oil experimental studies of moisture effects on the clay rocks including the relationship between suction and water content, reaction oil de- and re-hydration, and the self-sealing potential of the examined materials. The results indicate that the clay rocks react; very sensible to a moisture change. Wetting and drying caused significant swelling and shrinking. After re-saturation, highly damaged samples exhibited a very strong reduction in gas-permeability from 10(-16) -10(-17) m(2) to 10(-21)-10(-22) m(2), indicating a high self-sealing capacity of the studied argillaceous rocks.