Architecture and management of a geological repository - Andra

2 – General DescriptionThis section provides a global introduction to the geological context of the Meuse/Haute-Marne site,plus the various results obtained on the properties of Callovo-Oxfordian argillites.As indicated above, the characteristics of the clay formation, studied in particular by the undergroundresearch laboratory, contribute significantly to the achievement of the repository safety functions. Themain characteristics in this respect are its thickness, continuity, permeability, retention capacity andgeodynamic stability. The hydrogeological context on a larger scale also plays a part in the assessmentof long-term repository performance.The study of waste emplacement in a repository and the control of disturbance are also based onknowledge of other characteristics of the host formation: dip, depth and mechanical and thermalbehaviour.2.3.1 General presentation of the sector studiedGeologically speaking, the Meuse/Haute-Marne site belongs to the eastern rim of the Paris Basin; thelowest point of this basin corresponds to the Ile de France region. In the zone studied, the Paris Basinconsists of alternating layers of predominantly clay sediment and limestone; these layers weredeposited between 250 million and 135 million years ago ([6] - Volume 1).In detail, the sedimentary series more particularly concerned by the study comprises, from the bottomup (and from east to west at the outcrops):- the Dogger limestone formation resting on Liassic marls and clays,- the Callovo-Oxfordian argillite formation,- the middle to upper Oxfordian limestone formation,- Kimmeridge marls,- at the outcrop at the location of the site, Tithonian limestone (known as Calcaire du Barrois),- a few superficial Argilloarenaceous Cretaceous deposits thinly covering the highest points of thetopography.These sedimentary layers have a simple, monoclinal structure with a slight, regular dip of 1 to 1.5degrees to the north-west.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM44/495