Bentonite; Experimental methods; Finite Element Method; Numerical Modelling; Pore structure distribution; Water transfer mechanism; Experimental campaign; Hydro-mechanical; Mechanical response; Nuclear waste disposal; Numerical results; Pore-size distribution; Pores structure; Water transfer mechanisms; Geotechnical Engineering and Engineering Geology; Geology
Abstract :
[en] Several nuclear waste disposal concept designs take advantage of bentonite based materials to seal underground galleries and shafts. Safety assessment and long-term predictions of the material behaviour have been the main objective of a number of experimental campaigns and of constitutive models development. All these studies have underlined that the multi-porosity bentonite structure affects undeniably the strongly coupled hydro-mechanical processes taking place during water saturation. Due to this, in recent years, many classic experimental tests on unsaturated soils have been performed in conjunction with multi-scale observation techniques (for instance MIP, i.e. mercury intrusion porosimetry analises). Despite the well-known limitations of such observation methods, they provide interesting quantitative measurements in terms of pore diameters families, which differ by several orders of magnitude, and their distribution with respect to different assemblies' types (namely pellets mixtures and compacted bentonite blocks). On the other hand, very few studies have been focusing on the role of such pore size distributions with respect to the hydro-mechanical response, both from an experimental and a numerical point of view. The aim of this paper is to present the experimental campaign and the numerical modelling strategy adopted to analyse the role of different pore size distributions characterising MX-80 bentonite in different forms (i.e. 32 mm pellets mixture, 7 mm pellets mixture and compacted sample surrounded by gap) with same overall dry density during isochoric hydration tests. Taking advantage of multisensor-equipped cells and post-mortem analyses and of the finite element code LAGAMINE, the hydro-mechanical response of these bentonite assemblies is examined. Experimental and numerical outcomes result in good agreement and provide complementary information regarding the features of each assembly type.
Disciplines :
Civil engineering
Author, co-author :
Gramegna, Liliana; Université de Liège, Département ArGEnCo - Géotechnique, Géomécanique et Géologie de l'Ingénieur, Liège 1, Belgium
Bernachy-Barbe, Fabien; Université Paris-Saclay, CEA - Service d'Etude du Comportement des Radionucléides, Gif-sur-Yvette, France
Collin, Frédéric ; Université de Liège - ULiège > Urban and Environmental Engineering
Talandier, Jean; ANDRA - Agence Nationale pour la gestion des Déchets Radioactifs, Châtenay-Malabry, France
Charlier, Robert ; Université de Liège - ULiège > Département ArGEnCo
Language :
English
Title :
Pore size distribution evolution in pellets based bentonite hydration: Comparison between experimental and numerical results
EURATOM - European Atomic Energy Community [BE] ANDRA - Agence Nationale pour la Gestion des Déchets Radioactifs [FR] EU - European Union [BE]
Funding text :
This work was funded by the European project BEACON (project receiving funding from the Euratom research and training programme 2014–2018 under grant agreement No 745942 and the Agence Nationale de gestion des Déchets Radioactifs (Andra).
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