A model benchmark exercise for numerical analysis of the Callovo-Oxfordian claystone hydromechanical response to excavation operations

International audienceThe Callovo-Oxfordian claystone (COx) is considered as a potential geological formation to host an industrial radioactive waste repository in France, thanks to its favorable characteristics for radioactive waste containment, as it has a very low hydraulic conductivity, small molecular diffusion and significant retention capacity for radionuclide. A deep understanding of the thermo-hydro-mechanical (THM) behavior of the COx is a key issue for design of different repository structures and the safety calculations of the project. Several constitutive models have been developed/used in the framework of the R&D and simulation programs of Andra. These models aim to reproduce the THM behavior of COx under different repository situations and for different structures. A model benchmark exercise has been launched since 2012 to provide an overall view of the developed models, their basic assumptions, their mathematical descriptions, variables and parameters, and to investigate the consequences of these basic assumptions on the calculations results regarding to the experimental observations. Three main constitutive model families are considered; namely, visco-elasto-plastic models, damagemechanics based and computational homogenized (CHM) ones. Nine teams using different models have been participated to this benchmark exercise