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ALERT Poster Session - A 2nd gradient Thermo-Hydro-Mechanical model to investigate gas transfer processes in low-permeable media
Corman, Gilles; Collin, Frédéric
201930th ALERT Workshop (2019)
 

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Keywords :
Numerical Modelling; Excavation Damaged Zone; Strain localisation; Gas Migrations
Abstract :
[en] Nowadays, the deep geological disposal based on the multi-barriers confinement concept, is considered as one of the most promising solutions for the safe storage of radioactive wastes. Many Thermo-Hydro-Mechanical (THM) phenomena are likely to occur during the construction and the lifetime of the repository, which could alter the confining function of the different constituent layers. Among these, the underground excavation process tends to create a so-called Excavation Damaged Zone (EDZ) in the surrounding of the storage galleries, where the mechanical and hydraulic properties are affected [1]. For instance, the hydraulic permeability is increased compared to the sound rock formation. Moreover, during the exploitation of the system, a certain amount of gases, such as hydrogen could actually be generated in the nearfield of the repository due to the anoxic corrosion of the metal components, and could potentially lead to the alteration of the host rock behaviour. In light of this, the present work aims at developing a numerical tool within the finite element code LAGAMINE, able to reproduce simultaneously the development of strain localisation bands due to excavation and the multiphysical couplings associated with gas generation and migrations. This model includes on the one hand a THM part [2] to describe triphasic porous media under unsaturated and non-isothermal conditions. On the other hand, since the problem involving strain localisation is not well posed when modelled using classical medium, the local second gradient approach [3] is also integrated to the model. It helps avoiding the pathological mesh dependency by considering an enrichment of the continuum with microstructure effects through a regularizing internal length [4]. This model is subsequently used for reproducing two in situ gas injection tests (Experiments E4 and E5 performed in the framework of the MEGAS European project in the Underground Research Laboratory (URL) in Mol [5]) conducted in two distinct directions in the Boom Clay Formation, which is investigated by the Belgian National Radioactive Waste Management Agency (ONDRAF) as potential host rock for a deep geological disposal. The 2D plain strain simulations provide information about the fracture structure and permeability evolution due to the excavation, and about the stress state during a phase of pore pressures stabilization, and during a last phase of gas migrations.
Disciplines :
Civil engineering
Author, co-author :
Corman, Gilles ;  Université de Liège - ULiège > Département ArGEnCo > Géotechnique
Collin, Frédéric  ;  Université de Liège - ULiège > Département ArGEnCo > Géotechnique
Language :
English
Title :
ALERT Poster Session - A 2nd gradient Thermo-Hydro-Mechanical model to investigate gas transfer processes in low-permeable media
Alternative titles :
[en] Modèle 2nd gradient Thermo-Hydro-Mecanique pour étudier les processus de transferts de gas dans les milieux peu perméables
Publication date :
30 September 2019
Number of pages :
Format A0
Event name :
30th ALERT Workshop (2019)
Event organizer :
ALERT Geomaterials - Alliance of Laboratories in Europe for Education, Research and Technology
Event place :
Aussois, France
Event date :
du 30 septembre 2019 au 2 octobre 2019
Audience :
International
Funders :
ONDRAF - Organisme National des Déchets Radioactifs et des Matières Fissiles Enrichies [BE]
Commentary :
[1] Blümling P, Bernier F, Lebon P, Martin CD, The excavation damaged zone in clay formations time-dependent behaviour and influence on performance assessment. Phys Chem Earth, 32(8–14):588–599, 2007. [2] F. Collin, Couplages thermo-hydro-mecaniques dans les sols et les roches tendres partiellement saturés, thèse / mémoire, University of Liege, 2003. [3] B. Pardoen, S. Levasseur, and F. Collin, Using Local Second Gradient Model and Shear Strain Localisation to Model the Excavation Damaged Zone in Unsaturated Claystone, Rock Mech. Rock Eng., 48(2):691-714, 2015. [4] Chambon R, Caillerie D, El Hassan N. One-dimensional localisation studied with a second grade model. European Journal of Mechanics - A/Solids, 17 (4): 637–656, 1998. [5] G. Volckaert, L. Ortiz, P. De Canniere, M. Put, S. T. Horseman, J. F. Harrington, V. Fioravante, and M. Impey. MEGAS: modelling and experiments on GAS migration in repository host rocks. Final report phase 1. Technical report, Eur. Comm., [Rep.] EUR 16235 EN.,1995.
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