Numerical anisotropic modelling of a deep drift at the Meuse/Haute-Marne URL

International audienceThe development of nuclear energy raised the issue of radioactive waste disposal in deep geological formations. Clay formations in their natural state show very favorable confining conditions as repositories for radioactive waste due to their generally low values of hydraulic conductivity and significant retention capacity for radionuclides. Three clay formations in Europe are currently being studied in details as potential host rocks for high level radioactive waste disposal, i.e. the Boom Clay in Belgium, the Opalinus Clay in Switzerland and the Callovo- Oxfordian Claystone (COx) in France. Lastly, the French national radioactive waste management agency (Andra) started building the underground research laboratory (URL) at Bure in the Meuse district. Several specific in situ experiments were carried out with the main objectives in term of underground civil engineering to: (a) evaluate the geological environment of the future Deep Geological Repository (DGR), (b) collect data from the clay formation in order to assess the performances of the future DGR, (c) test and demonstrate the feasibility of the future DGR. The feedback of these experiments and in situ measurements as well as the numerous theoretical analyzes and numerical modeling works undertaken on the COx allowed to identify the key mechanisms (mainly in the framework of THM processes) governing the behavior of the COx [1]. In addition to the THM processes and the associated parameters, it appears necessary to consider the anisotropies (mechanical, hydraulic and thermal) of such rock, but also its time-dependent behavior. This paper deals with these issues