Mehrdokht Mohajerani

On the Resaturation of Swelling Claystone

The hydration of unsaturated Callovo-Oxfordian (COx) claystone specimens from the 490 m deep URL of Bure in France has been investigated in high stress oedometers by conducting hydration tests on unsaturated specimens under stress values that were lower, equal and higher than the in-situ stress (resaturation of swelling clays should be done under in-situ stress to avoid any swelling that would affect their structure). Hydration tests always exhibited a swelling behaviour, even under stresses higher than in-situ. Based on other published experimental evidence, it is suggested that this swelling behaviour is due to damage, since the presence of cracks within claystones are known to enhance the swelling properties of claystones. A procedure of saturating claystone samples in the oedometer with limited swelling is then proposed.

The Thermal Volume Change of Opalinus Clay

Deep geological storage of high activity radioactivity waste is an option considered in many countries. In Belgium, France and Switzerland, clays and claystones are considered as possible geological barriers. In this context, the NAGRA agency of Switzerland is operating an Underground Research Laboratory (URL) of Mont Terri excavated in the Opalinus Claystone.