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Article Dans Une Revue Near Surface Geophysics Année : 2009

Preferential fluid flow pathways in embankment dams imaged by self-potential tomography

Résumé

We invert self-potential data in order to locate anomalous water flow pathways in dams and embankments and to estimate the seepage velocity. The inversion of the self-potential data is performed using the modified singular value decomposition for the inverse problem using a linear formulation of the forward problem. The kernel is solved numerically accounting for the topography of the system and the resistivity distribution, which is independently obtained through electrical resistance tomography. A prior constraint based on finite element modelling of ground water flow can also be used to provide a prior source current density model if needed. This self-potential tomography approach is first validated with a synthetic case study showing how the position of a preferential fluid flow pathway can be retrieved from self-potential and resistivity data and how the seepage velocity can be obtained inside one order of magnitude. This methodology is then applied to a test site corresponding to a portion of an embankment dam along the Rhône River in France. Two self-potential maps (with 1169 and 2076 measurements, respectively) and four resistivity tomograms are used to locate a leak. One self-potential profile and one resistivity profile are used together to perform the 2D inversion of the self-potential data to locate the anomalous leakage at depth and to estimate the flow rate. The depth at which the preferential fluid flow pathway is located, according to self-potential tomography, agrees with an independent geotechnical test using the Perméafor. This demonstrates the usefulness of this methodology to detect preferential water channels inside the body of a dam.

Dates et versions

insu-00498501 , version 1 (07-07-2010)

Identifiants

Citer

A. Boleve, André Revil, F. Janod, J. L. Mattiuzzo, J.-J. Fry. Preferential fluid flow pathways in embankment dams imaged by self-potential tomography. Near Surface Geophysics, 2009, 7 (5-6), pp.447-462. ⟨10.3997/1873-0604.2009012⟩. ⟨insu-00498501⟩
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