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| Titel |
Laboratory measurements of dielectric permittivity and electrical conductivity as a function of water content of soils in the intermediate frequency domain (100 kHz - 10 MHz) |
| VerfasserIn |
Pauline Kessouri, Fayçal Rejiba, Cyril Schamper, Alain Tabbagh |
| 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 |
250042523
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| Zusammenfassung |
| Abstract:
This study focuses on the measurement of the electrical properties of soils in the
intermediate frequency range (100 kHz – 10 MHz). The mapping of the soil moisture,
necessitating the mapping the electrical properties in situ, requires preliminary laboratory
measurements conducted under controlled conditions. The effective electrical conductivity
Ï(Ï) is usually measured in the low frequency range (< 100 kHz), and mainly related to the
clay content of the soil. The effective dielectric permittivity É(Ï) is generally obtained at high
frequency (> 50 MHz), and related to the water content of the soil. In the intermediate
frequency range both parameters depend on water and clay content. The determination of the
water content thus requires estimating the effect of the clay content. To reach that goal,
a series of laboratory measurements on artificial and natural samples have been
undertaken.
These laboratory measurements were carried out using a capacitive cell and an electrical
square quadripole. The complex effective relative dielectric permittivity É* is measured with
the capacitive cell, and defined as follow: É*=É’(Ï)+i[É”(Ï) - Ï(Ï)/Ï.É0], where Ï
corresponds to the pulsation and É0 is the dielectric constant of the vacuum. The objective is
to study the contribution of water and clay content on the following parameters: É’(Ï) the
real relative dielectric permittivity, É”(Ï) the dielectric losses, and Ï(Ï) the real
electrical conductivity. Moreover, using the electrical square quadripole enables
to measure the “direct-current” electrical conductivity ÏDC. These two types of
measurements allow to discriminate the factor linked with conduction phenomena (equal to
Ï’(Ï)/Ï.É0) in the imaginary part of É*, strongly dependant of the clay fraction in the
sample.
Measures on sandy samples, coupled with theoretical modeling (effective medium
theory) show that the H.F. relationship between É’(Ï) and the water content can
be extended until 1 MHz. In presence of clay, it is possible, using the measured
ÏDC, to separate the factor linked with conduction phenomena from the dielectric
losses.
Keywords:
dielectric permittivity, electrical conductivity, water content, capacitive cell measurements |
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