The characteristics of the Opalinus Clay investigated in the Mont Terri underground rock laboratory in Switzerland

In the Mont Terri Rock Laboratory, eleven organisations from six countries (ANDRA and IPSN from France) are investigating jointly a Mesozoic shale formation, the Opalinus Clay. The aims of the research programme are to analyse its hydrogeological, geochemical and rock mechanical properties, the changes induced by the excavation of galleries, by heat-generating waste and by engineered barriers, and to evaluate and improve appropriate investigation techniques. The results of a series of experiments indicate that, at a convenient site, the investigated or similar clay formations could be favourable for hosting a safe repository for radioactive waste. 2002 Academie des sciences/Editions scientifiques et medicales Elsevier SAS.