Article (Scientific journals)
Using local second gradient model and shear strain localisation to model the excavation damaged zone in unsaturated claystone
Pardoen, Benoît; Levasseur, Séverine; Collin, Frédéric
2015In Rock Mechanics and Rock Engineering, 48 (2), p. 691-714
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Keywords :
Numerical modelling; Fracturing; Excavation damaged zone; Strain localisation; Unsaturated soil; Gallery ventilation
Abstract :
[en] The drilling of galleries induces damage propagation in the surrounding medium and creates, around them, the excavation damaged zone (EDZ). The prediction of the extension and fracture structure of this zone remains a major issue, especially in the context of underground nuclear waste storage. Experimental studies on geomaterials indicate that localised deformation in shear band mode usually appears prior to fractures. Thus, the excavation damaged zone can be modelled by considering the development of shear strain localisation bands. In the classical finite element framework, strain localisation suffers a mesh-dependency problem. Therefore, an enhanced model with a regularisation method is required to correctly model the strain localisation behaviour. Among the existing methods, we choose the coupled local second gradient model. We extend it to unsaturated conditions and we include the solid grain compressibility. Furthermore, air ventilation inside underground galleries engenders a rock– atmosphere interaction that could influence the damaged zone. This interaction has to be investigated in order to predict the damaged zone behaviour. Finally, a hydromechanical modelling of a gallery excavation in claystone is presented and leads to a fairly good representation of the EDZ. The main objectives of this study are to model the fractures by considering shear strain localisation bands, and to investigate if an isotropic model accurately reproduces the in situ measurements. The numerical results provide information about the damaged zone extension, structure and behaviour that are in very good agreement with in situ measurements and observations. For instance, the strain localisation bands that develop in chevron pattern during the excavation and rock desaturation, due to air ventilation, are observed close to the gallery.
Research center :
ArGEnCo
Disciplines :
Civil engineering
Author, co-author :
Pardoen, Benoît ;  Université de Liège - ULiège > Département ArGEnCo > Géomécanique et géologie de l'ingénieur
Levasseur, Séverine ;  Université de Liège - ULiège > Département ArGEnCo > Géomécanique et géologie de l'ingénieur
Collin, Frédéric  ;  Université de Liège - ULiège > Département ArGEnCo > Géotechnique
Language :
English
Title :
Using local second gradient model and shear strain localisation to model the excavation damaged zone in unsaturated claystone
Publication date :
2015
Journal title :
Rock Mechanics and Rock Engineering
ISSN :
0723-2632
eISSN :
1434-453X
Publisher :
Springer Science & Business Media B.V.
Volume :
48
Issue :
2
Pages :
691-714
Peer reviewed :
Peer Reviewed verified by ORBi
Funders :
F.R.S.-FNRS - Fonds de la Recherche Scientifique [BE]
Available on ORBi :
since 17 June 2014

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