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| Titel |
Electrokinetics dependence on water-content: laboratory and field approach |
| VerfasserIn |
Vincent Allègre, Pascale Sénéchal, François Lehmann, Clarisse Bordes, Laurence Jouniaux, Pascal Sailhac, Maksim Bano |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250041500
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| Zusammenfassung |
| Electrokinetics results from the coupling between the water flow and the electrical current
through the electrokinetic coefficient. The Self-Potential (SP) method, which is based on this
phenomenon, is currently used to investigate shallow transport in the vadose zone. Thus, the
understanding of the electrokinetic coefficient behaviour in unsaturated conditions is crucial
to interpret such methods. Empirical and theoretical models proposed in the literature to
describe this behaviour are still discussed. Consequently, physical processes involved in the
electrokinetic coefficient behaviour in unsaturated conditions need to be futher
investigate.
We propose here to study the electrokinetics dependence on water content through an
experimental approach and the numerical solving of the Richards’ equation. We show several
continuous records of the electrokinetic coefficient as a function of water saturation. We
found that the normalized electrokinetic coefficient behaviour in unsaturated conditions is
more complex than it was previously proposed. Indeed, we first observed its increasing with
decreasing water saturation. After it reaches a maximum, identified around 80 % of
water saturation, it begins to decrease with decreasing saturation. It is an important
result since previous works predicted a monotically decreasing of the electrokinetic
coefficient with decreasing saturation. We found that the normalized value of the
measured electrokinetic coefficient could be two orders of magnitude greater than the
classical value in saturated conditions, Csat. We performed several experiments and
tried to invert the electrokinetic coefficient data and interpret it in terms of physical
processes.
We also propose a field study through several geophysical methods, as electrical
resistivity tomography, seismoelectrics, and GPR, in order to combine the results in terms of
water-content dependence in soils. |
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