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Modelling the behaviour of bentonite pellet-powder mixtures upon hydration from dry granular state to saturated homogeneous state
Abstract Bentonite pellet-powder mixtures are candidate materials for sealing the galleries in deep geological repositories for radioactive waste. In the present work, swelling pressure tests are performed on pellet-powder mixtures with different powder contents. Results highlight the influence of the initial granular structure on the mechanical behaviour of pellet-powder mixtures. In mixtures with a low density powder in the inter-pellet porosity, the macroscopic response of pellet-powder mixtures is identical to that of a pellet assembly with no powder. A model is proposed to describe the hydromechanical behaviour of pellet-powder mixtures. The formulation considers two distinct states of the material, Granular and Continuous. In the Granular state, the pellets control the mechanical behaviour of the mixture. In the Continuous state, both pellets and powder contribute to the mechanical behaviour of the mixture. In the Granular domain, the material behaviour is described by constitutive laws proposed after a numerical study using Discrete Element Method. In the Continuous domain, the material behaviour is described by a modified Barcelona Basic Model. Transition between the two domains depends on the density of the powder phase and suction. The model is implemented in a Finite Element Method code, and the swelling pressure tests performed in the laboratory are simulated with a single set of parameters. These results improve the knowledge on the behaviour of bentonite pellet-powder mixtures during hydration in repository conditions.
Highlights Swelling pressure tests have been carried out on three different bentonite pellet-powder mixtures. The initial granular structure controls the evolution of swelling pressure if the density of the powder phase is low. The behaviour of pellet assemblies has been studied under isotropic compression through DEM simulations. Based on experimental and DEM results, a conceptual model for pellet-powder mixture has been proposed. The numerical results generally reproduced very well the experimental results, using a single set of parameters.
Modelling the behaviour of bentonite pellet-powder mixtures upon hydration from dry granular state to saturated homogeneous state
Abstract Bentonite pellet-powder mixtures are candidate materials for sealing the galleries in deep geological repositories for radioactive waste. In the present work, swelling pressure tests are performed on pellet-powder mixtures with different powder contents. Results highlight the influence of the initial granular structure on the mechanical behaviour of pellet-powder mixtures. In mixtures with a low density powder in the inter-pellet porosity, the macroscopic response of pellet-powder mixtures is identical to that of a pellet assembly with no powder. A model is proposed to describe the hydromechanical behaviour of pellet-powder mixtures. The formulation considers two distinct states of the material, Granular and Continuous. In the Granular state, the pellets control the mechanical behaviour of the mixture. In the Continuous state, both pellets and powder contribute to the mechanical behaviour of the mixture. In the Granular domain, the material behaviour is described by constitutive laws proposed after a numerical study using Discrete Element Method. In the Continuous domain, the material behaviour is described by a modified Barcelona Basic Model. Transition between the two domains depends on the density of the powder phase and suction. The model is implemented in a Finite Element Method code, and the swelling pressure tests performed in the laboratory are simulated with a single set of parameters. These results improve the knowledge on the behaviour of bentonite pellet-powder mixtures during hydration in repository conditions.
Highlights Swelling pressure tests have been carried out on three different bentonite pellet-powder mixtures. The initial granular structure controls the evolution of swelling pressure if the density of the powder phase is low. The behaviour of pellet assemblies has been studied under isotropic compression through DEM simulations. Based on experimental and DEM results, a conceptual model for pellet-powder mixture has been proposed. The numerical results generally reproduced very well the experimental results, using a single set of parameters.
Modelling the behaviour of bentonite pellet-powder mixtures upon hydration from dry granular state to saturated homogeneous state
Darde, Benjamin (author) / Dangla, Patrick (author) / Roux, Jean-Noël (author) / Pereira, Jean-Michel (author) / Talandier, Jean (author) / Vu, Minh Ngoc (author) / Tang, Anh Minh (author)
Engineering Geology ; 278
2020-09-26
Article (Journal)
Electronic Resource
English
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