ABSTRACT:

In order to understand and to predict the response of EBS, we simulate a clay-rock repository case considering chemo-mechanical coupling, in which chemical changes affect the mechanical behavior of the bentonite through the evolution of volume fraction of smectite, exchangeable cation concentration, and ionic strength (via osmotic suction). The mechanical model for the buffer is based on an existing double-structure formulation that accounts for the deformations at two structure levels, microstructure and macrostructure. Chemical effects are defined and coupled with the mechanical model at the microstructural level. This new model is implemented into a numerical simulator based on sequential coupling of the reactive transport simulator TOUGHREACT and the geomechanical simulator FLAC3D. The simulator denoted TOUGHREACT-FLAC is used to model the EBS behavior to predict the effects of chemical reactions on the stress evolution for generic case of a repository in a clay host rock. The simulation results illustrate the phenomenon of chemical-mechanical interactions and geomechanical performance of the repository to evaluate the potential deterioration of EBS bentonite, and to support the decision making in the design of a nuclear waste repository.

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