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Modélisation multi-échelle des transferts en milieux fracturés : application au site de Äspö (Suède)

Abstract : In the field of nuclear waste storage, the geological barrier is the last transfer zone for radio-elements. Since fractures are to be found in geological media, especially for granitic fractured media, special emphasis is put on improving modeling approaches to transfer processes in fractured media. It remains a challenging task due to the large contrasts in the properties of different units of the medium, the geometrical complexity of the system and strong level of uncertainties for flow and transport parameters. In addition, for post closure natural flow conditions, flow is slow and diffusion processes play a major role contributing to the retention of the plume. In this context, a Smeared Fractures approach was developed for a Mixed and Hybrid Finite Element scheme and implemented in our code, Cast3M. This approach allows for explicit representation of major fractures while adopting an homogenized representation of lower levels of fracturation. This Smeared Fracture approach doesn't require explicit meshing of the complex fracture network geometry. The fractured block is represented on regular mesh, the presence of the fracture being taken into account through an heterogeneous field of parameters. Considering conservation of flow and mass fluxes for each fracture, these parameters are derived. The performances of Smeared Fractures approach are comparable to discrete modeling for flow and presents in addition the advantage of taking full 3D matrix block geometry into account for transport. The size of the mesh as well as temporal discretization have to comply with criteria that were established. Nevertheless, within these boundaries coarser discretization is possible allowing for notable computing costs. The validation and qualification phase was conducted for 2D and 3D cases. These include results on synthetics and realistic systems, for different flow regimes and parameter values. The approach is finally applied on several cases from the Äspö site, Sweden.
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https://tel.archives-ouvertes.fr/tel-00218275
Contributor : Andre Fourno <>
Submitted on : Saturday, January 26, 2008 - 12:56:53 AM
Last modification on : Monday, May 4, 2020 - 11:04:17 AM
Long-term archiving on: : Thursday, April 29, 2010 - 4:46:03 PM

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  • HAL Id : tel-00218275, version 1

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Andre Fourno. Modélisation multi-échelle des transferts en milieux fracturés : application au site de Äspö (Suède). Hydrologie. Université de Poitiers, 2005. Français. ⟨tel-00218275⟩

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