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Effects of the initial granular structure of clay sealing materials on their swelling properties: experiments and DEM simulations

The present study focuses on the material behaviour before homogenisation. A grain-scale experimental characterisation is first performed in the laboratory. | Effects of the initial granular structure of clay sealing materials on their swelling properties experiments and DEM simulations EPJ Nuclear Sci. Technol. 6 1 2020 Nuclear Sciences B. Darde et al. published by EDP Sciences 2020 amp Technologies https doi.org 10.1051 epjn 2019059 Available online at https www.epj-n.org REGULAR ARTICLE Effects of the initial granular structure of clay sealing materials on their swelling properties experiments and DEM simulations Benjamin Darde1 Anh Minh Tang1 Jean-Noël Roux1 Patrick Dangla1 Jean-Michel Pereira1 Jean Talandier2 and Minh Ngoc Vu2 1 Université Paris-Est Laboratoire Navier UMR 8205 Ecole des Ponts ParisTech Ifsttar CNRS 6-8 avenue Blaise Pascal Cité Descartes 77455 Marne-la-Vallée Cedex 2 France 2 Andra R amp D 1-7 rue Jean Monnet Parc de la Croix-Blanche 92298 Châtenay-Malabry Cedex France Received 20 October 2019 Accepted 8 November 2019 Abstract. Pellet-based expansive clay materials are considered as a sealing material for closing the galleries in radioactive waste disposal concepts. In repository conditions the granular mixture progressively homogenises upon hydration by the host rock pore water. The present study focuses on the material behaviour before homogenisation. A grain-scale experimental characterisation is first performed in the laboratory. A model describing the hydromechanical behaviour of a pellet is proposed based on the experimental results. Then suction-controlled swelling pressure tests are performed in the laboratory. Using Discrete Element Method DEM and the model proposed for a single pellet the tests are successfully simulated. It is highlighted that i the swelling pressure evolves in two phases in the investigated suction range controlled by the granular structure of the mixture ii wall effects at the laboratory scale affects the material response iii measurement variability associated to the sensor diameter is non-negligible iv DEM is a valuable tool able to provide insight into the material