Research performed by Gilles Corman.
The scope of the PhD thesis covers the numerical investigation of gas transfers both in the EDZ and in the sound rock mass, with the objective of developing, validating and applying numerical tools able to reproduce these gas transfer mechanisms.
Gas migrations in EDZ
Considering first gas migrations in the EDZ, a numerical model is elaborated in such a way as to be able to reproduce simultaneously the excavation damage around the gallery as a strain localisation process in shear band mode, and the multiphysics couplings associated with gas generation and migrations.
This model is subsequently used for reproducing small scale applications (in situ gas injection tests) and large scale applications (storage gallery).
Gas migrations in sound rock layers
As for gas migrations in the sound rock layers, a multi-scale approach will be envisaged. The development of localised gas pathways under increasing gas pressure will indeed require to consider a lower scale taking more particularly the multi-scale interactions proper to gaseous migration in an undisturbed confined medium into account. The model will be built in the framework of the finite element squared method, using a fine scale Representative Elementary Volume (REV) for the pore network which makes possible not to model all the microstructural details for the full domain. The response to loading of the REV is linked to the macroscale by employing homogenisation equations. And finally, the boundary value problems are solved at both scales using a finite element method.
Through the proposed innovative developments, the challenge is to better understand the impacts of gas transfers on the behaviour of argillaceous materials and their insulation characteristics, with a view to improving the multi-barrier confinement concept, and thus the long-term management of nuclear wastes.