Experimental and numerical analysis of dielectric polarization effects in near‐surface earth materials in the 100 Hz–10 MHz frequency range: First interpretation paths
Résumé
The recent developments of electromagnetic induction and electrostatic
prospection devices dedicated to critical zone surveys in both rural and urban
contexts necessitate improving the interpretation of electrical properties through
complementary laboratory studies. In a first interpretation step, the various
experimental results obtained in the 100 Hz–10 MHz frequency range can be
empirically fitted by a simple six-term formula. It allows the reproduction of the
logarithmic decrease of the real component of the effective relative permittiv-
ity and its corresponding imaginary component, the part associated with the
direct current conductivity, one Cole–Cole relaxation and the real and imaginary
components of the high-frequency relative permittivity. For elucidating physical
phenomena contributing to both the logarithmic decrease and the observed
Cole–Cole relaxation, we first consider the Maxwell–Wagner–Sillars polariza-
tion. Using the method of moments, we establish that this continuous medium
approach can reproduce a large range of relaxation characteristics. At the micro-
scopic scale, the possible role of the rotation of the water molecules bound to
solid grains is then investigated. In this case, contrary to the Maxwell–Wagner–
Sillars approach, the relaxation parameters do not depend on the external
medium properties
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