Chapter 16 Dielectric Permittivity and Moisture Content

Abdel-Mohsen Onsy Mohamed
Evan K. Paleologos

Document Type

Book Chapter

Source of Publication

Fundamentals of Geoenvironmental Engineering

Publication Date

1-1-2018

Abstract

This chapter discusses the concept of soil dielectrics, available techniques for the determination of soil dielectric permittivity and soil moisture content, and the associated theoretical background for a better understanding of the measured soil dielectric property and the moisture content. The design stages of the Time Domain Reflectometry (TDR) system and the methods used to characterize the reflected signal are discussed. Important probe design factors, such as probe length, rod diameter, spacing between the rods, sampling volume, connector type, connector correction, and probe robustness, that influence the reflected signals are evaluated. Laboratory measurement techniques for dielectric permittivity and bulk electrical conductivity are also deliberated. These two properties are often obtained by direct analysis of the TDR waveforms in the time domain. However, since much more information is contained in TDR waveforms, using the extended Debye model, the inverse modeling of TDR waveform to extract information about the frequency dependence of the soil dielectric permittivity, is explained. To represent the macroscopic dielectric property of a soil by its individual components, the widely used mixing models that relate dielectric constant and soil moisture content, are assessed. The influences of physicochemical properties, such as bound water content, capillary and free water, saline water solution, mineralogy, bentonite content, clay content, soil texture, moisture content, soil density, volcanic soils, and nonaqueous phase liquid solutions, on dielectric permittivity of soils are analyzed. The various moisture content prediction models such as empirical models, dielectric mixing, and physical models, are discussed. The impact of the physicochemical soil parameters on the validity of these models is also emphasized.

Publisher

Elsevier

Volume

Soil Sci. Soc. Am. J. 49 1985

Disciplines

Environmental Engineering

Indexed in Scopus

no

Open Access

no

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