Hydromechanical behaviour of bentonite under in situ conditions.
Event details
| Date | 22.09.2015 |
| Hour | 14:00 › 15:00 |
| Speaker | Anne-Catherine Dieudonné, PhD student, Univ. of Liège, Belgium |
| Location | |
| Category | Conferences - Seminars |
In 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 create a zone of low permeability that is able to limit water flow around the excavated galleries, and thereby delay the release of radionuclides to the biosphere.
Bentonite-based materials are usually manufactured and emplaced at their hygroscopic water content. Under in situ conditions, the material experiences hydration and swells. During the saturation process, technological gaps between the engineered barrier and the host rock are filled. Contact between the bentonite barrier and the host rock is progressively reached and results in the development of a swelling pressure against the gallery wall.
The present research aims at developing a hydromechanical model for compacted bentonite under in situ conditions. More precisely, the presentation addresses the following aspects
• The implementation of the Barcelona Basic Model in the finite element code Lagamine. The model is used to reproduce the large strains observed in compacted bentonites upon wetting.
• The extension of the existing hydromechanical formulation to include coupling between
- The water retention behaviour and the evolving material micro- and macrostructure;
- The permeability and the material macrostructure.
• 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 interfaces once contact is achieved.
The hydromechanical behaviour of a bentonite buffer submitted to hydration under in situ conditions is studied numerically using Lagamine. The investigated problem is directly related to the set of experiments PGZ2 developed in Andra’s underground research laboratory.
More precisely, the modelling concerns in the excavation of a small-diameter gallery within the Callovo-Oxfordian claystone (France). A block 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.
Numerical results of the problem are analysed in detail and compared to experimental data. The importance of the various hydromechanical coupling is investigated.
Bentonite-based materials are usually manufactured and emplaced at their hygroscopic water content. Under in situ conditions, the material experiences hydration and swells. During the saturation process, technological gaps between the engineered barrier and the host rock are filled. Contact between the bentonite barrier and the host rock is progressively reached and results in the development of a swelling pressure against the gallery wall.
The present research aims at developing a hydromechanical model for compacted bentonite under in situ conditions. More precisely, the presentation addresses the following aspects
• The implementation of the Barcelona Basic Model in the finite element code Lagamine. The model is used to reproduce the large strains observed in compacted bentonites upon wetting.
• The extension of the existing hydromechanical formulation to include coupling between
- The water retention behaviour and the evolving material micro- and macrostructure;
- The permeability and the material macrostructure.
• 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 interfaces once contact is achieved.
The hydromechanical behaviour of a bentonite buffer submitted to hydration under in situ conditions is studied numerically using Lagamine. The investigated problem is directly related to the set of experiments PGZ2 developed in Andra’s underground research laboratory.
More precisely, the modelling concerns in the excavation of a small-diameter gallery within the Callovo-Oxfordian claystone (France). A block 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.
Numerical results of the problem are analysed in detail and compared to experimental data. The importance of the various hydromechanical coupling is investigated.
Practical information
- General public
- Free
Organizer
- LMS-ENAC
Contact
- B. Tinguely, LMS 32315