This is probably because geological examples demonstrate the long-term confinement efficiency of clay-rich layers that public and private bodies involved in the management of various types of wastes or effluents have been interested in clay science and more precisely in the evaluation of the THMC properties of clays and clay formations. Indeed, accumulations or deposits of both mineral and energy resources are often preserved over geological times thanks to surrounding clay layers. Thus, whatever the geological context and the waste to be confined, natural and engineered clay barriers appear as system components of paramount importance. Thus, numerous national and international programs dealing with long-term storage for hazardous materials or geological CO2sequestration were launched. Some of them benefited from demonstration platforms or dedicated underground laboratories which allowed observations and experimentations to be conducted at different scales, conceptual models to be constructed and major progresses on clay reactivity to be obtained.However, we need to further assess the potential effects of the THMC solicitations associated with repository or sequestration conditions on the containment properties of natural or engineered materials. To reach such goals, the characterization, from the micrometer to the nanometer scale, of the structure of clay materials, the study of the individual physico-chemical phenomena involved and the development of codes and solvers for their simulation, are major issues for improving behavior models of the repository materials, clarifying the terms of transfer of hazardous elements and optimizing repositories architectures and components.Those THMC processes are necessarily integrated in a complex phenomenology which requires to manage couplings, the intensity and complexity of which vary in time and space. For example, understanding the healing mechanisms of clays cannot be based on a simple mechanical approach, but requires to control saturation conditions and to represent at a microscopic scale the petrophysical behavior of clays.

Issues related to thermo-hydro-chemico-mechanical processes for the design and safety evaluation of underground repositories and storages

248th National Meeting (2014)

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