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Theses

Écoulements dans les Fractures Ouvertes

Abstract : The first part of this thesis addresses a study of the geometry of rough fractures that have been obtained through controlled fracturing of granite and sandstone blocks. The surfaces are recorded using a specially deviced profiler, which allows mechanical and optical measurement. The recordings are well described by an isotropic self-affine model. The persistence of the correlations is significantly smaller for sandstone than it is for granite. In a second part, we study how the flow through a rough fracture is influenced by the roughness of the fracture walls, when inertial effects can be neglected. An experimental setup allows to observe a significant dependence of the fracture permeability on the orientation of the effective pressure gradient. A numerical model confirms these observations, and allows to interpret this hydraulic anisotropy in terms of flow channeling. Channeling is controlled by large scale heterogeneities in the aperture field; the importance of these heterogeneities is greatly dependent on the matching of the two walls at large scales. In a third part, a fracture filled with a gouge is modelled as a 2-dimensional porous medium made out of a single layer of glass beads. The downward displacement of a wetting fluid by air is studied experimentally in such a medium. By adjusting the Darcy velocity, we tune the intensity of the viscous forces and systematically study the transition between a regime where the displacement of the interface between the two fluids is stabilized by gravity, to a regime where the roughness of the interface increases infinitely. Capillary effects, which are inhomogeneous in the porous medium, drive the local dynamics of the displacement. Using the percolation theory, we predict the instability and a scaling law for the front width under stable displacement. These predictions are verified experimentally.
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https://tel.archives-ouvertes.fr/tel-00008477
Contributor : Yves Méheust <>
Submitted on : Wednesday, February 16, 2005 - 3:10:54 PM
Last modification on : Thursday, October 29, 2020 - 3:01:33 PM
Long-term archiving on: : Thursday, September 23, 2010 - 3:52:22 PM

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  • HAL Id : tel-00008477, version 3

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Yves Méheust. Écoulements dans les Fractures Ouvertes. Hydrologie. Université Paris Sud - Paris XI, 2002. Français. ⟨tel-00008477v3⟩

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