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SUMMARY:Hydromechanical behaviour of bentonite under in situ conditions.
DTSTART:20150922T140000
DTEND:20150922T150000
DTSTAMP:20261003T205459Z
UID:2dc880371ba8cc00e20b7005c989c5095167390c8da87bef74dfcbbd
CATEGORIES:Conferences - Seminars
DESCRIPTION:Anne-Catherine Dieudonné\, PhD student\, Univ. of Liège\, Be
 lgium\nIn the context of deep geological repositories for nuclear waste\, 
 particular attention is paid to the behaviour of bentonite-based materials
  in relation to their use as engineered barriers. The objective is to crea
 te a zone of low permeability that is able to limit water flow around the 
 excavated galleries\, and thereby delay the release of radionuclides to th
 e biosphere.\nBentonite-based materials are usually manufactured and empla
 ced at their hygroscopic water content. Under in situ conditions\, the mat
 erial experiences hydration and swells. During the saturation process\, te
 chnological gaps between the engineered barrier and the host rock are fill
 ed. Contact between the bentonite barrier and the host rock is progressive
 ly reached and results in the development of a swelling pressure against t
 he gallery wall.\nThe present research aims at developing a hydromechanica
 l model for compacted bentonite under in situ conditions. More precisely\,
  the presentation addresses the following aspects\n• The implementation 
 of the Barcelona Basic Model in the finite element code Lagamine. The mode
 l is used to reproduce the large strains observed in compacted bentonites 
 upon wetting.\n• The extension of the existing hydromechanical formulati
 on to include coupling between\n- The water retention behaviour and the ev
 olving material micro- and macrostructure\;\n- The permeability and the ma
 terial macrostructure.\n• The use of a hydromechanical interface element
  to reproduce the behaviour of technological gaps before reaching contact 
 between the materials\, as well as the hydromechanical behaviour of interf
 aces once contact is achieved.\nThe hydromechanical behaviour of a bentoni
 te buffer submitted to hydration under in situ conditions is studied numer
 ically using Lagamine. The investigated problem is directly related to the
  set of experiments PGZ2 developed in Andra’s underground research labor
 atory.\nMore precisely\, the modelling concerns in the excavation of a sma
 ll-diameter gallery within the Callovo-Oxfordian claystone (France). A blo
 ck of compacted bentonite is then placed in the gallery and hydration from
  the host rock is allowed. The difference in diameters between the gallery
  and the bentonite plug yields technological gaps. The existence of these 
 technological gaps is explicitly taken into account and modelled using the
  coupled interface finite element.\nNumerical results of the problem are a
 nalysed in detail and compared to experimental data. The importance of the
  various hydromechanical coupling is investigated.
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STATUS:CONFIRMED
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