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Theses

Mesure in situ et modélisation de l'hétérogénéité des écoulements dans les milieux géologiques

Abstract : The starting point of this work is the following observation: predictive models of flow and solute
transfer in the subsurface, which are often based on homogeneous porous media type of
representation, are not adapted to natural systems that are characterized by highly heterogeneous
velocity fields at all scales. The current high uncertainty in the prediction of flow and solute transfer
and residence times in these systems is related not only to the uncertainty in model parameter
estimation but also to the uncertainty in the relevance of the models themselves, which is related to the
hypothesis made concerning the representation of the distribution of fluid velocities. To tackle this
problem, the principal objectives of this PhD work was (i) to develop in situ measurement methods
adapted to the characterization of the organization and heterogeneity of the flow field, and (ii) to carry
on a theoretical study on the representation of the flow field organization in predictive models. This
work was done within the framework of the national network of hydrogeological sites ORE H+ and
the European projects SALTRANS (2000-2004) and ALIANCE (2001-2005).
Three main results were obtained. (1) We first demonstrated the fractal nature of flow in fractured
aquifer, from a scaling analysis of pumping tests. This approach allows defining an equivalent model
that is consistent with the mean hydraulic behaviour of a natural site over a large range of temporal
and spatial scales. (2) Concerning the experimental characterization of the flow velocity variability, we
used borehole flow velocity measurement devices in collaboration with Frederick Paillet (University
of Maine, USA). We proposed and tested a method of inversion of these measurements to image flow
paths and quantify there hydraulic properties at different scales in field sites. (3) Finally, we developed
a new method to quantify the flow field organization, based on numerical simulations of flow and
solute transport in heterogeneous permeability fields. The results obtained concerning the detailed
analysis of the flow field correlation structure allow re-examining the hypothesis made in solute
transport models, in order to progress towards a realistic representation of the velocity field in these
models.
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Theses
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https://tel.archives-ouvertes.fr/tel-00012050
Contributor : Isabelle Dubigeon <>
Submitted on : Tuesday, March 28, 2006 - 1:37:12 PM
Last modification on : Friday, April 5, 2019 - 8:03:26 PM
Long-term archiving on: : Saturday, April 3, 2010 - 9:05:48 PM

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  • HAL Id : tel-00012050, version 1

Citation

Tanguy Le Borgne. Mesure in situ et modélisation de l'hétérogénéité des écoulements dans les milieux géologiques. Hydrologie. Université Rennes 1, 2005. Français. ⟨tel-00012050⟩

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