Dielectric measurements of five different soil textural types as functions of frequency and moisture content

Abstract

Open-circuit coaxial transmission-line sample holders were used to determine the electromagnetic dielectric properties of five soil textural types as functions of moisture level content and frequency. A brief outline of the theoretical basis is given for the open-circuit method along with the measurement system and the sample preparation. Experimental results are given for the different soil textural types for moisture levels ranging from 0 to 48 percent and for test frequencies ranging from 300 to 9300 MHz.

Feasibility study on the use of a microwave system for the nondestructive evaluation of historic adobe structures

“…In the absence of any observable changes in wall roughness, thickness, or density, it is assumed the moisture content is steadily decreasing over this vertical distance. Measurements made at NBS with sandy loam indicate that this change in dielectric constant corresponds roughly to a 3 percent change in moisture content [12,13]. This contrasts with the horizontal series 5 measurements that show extremely constant average dielectric constant values of about 6.7 for the complete distance.…”

“…The dielectric constant can also be affected by changes in moisture content or density with respect to the wall area initially used to determine e-j [12]. This means a measurement of the change in moisture content of a wall can be made as the surface is scanned.…”

“…This should be within the dynamic range of an FM-CW system as used in this work. This change in dielectric constant corresponds to a density change in adobe of approximately 0.2 percent or a moisture change of about 0.1 percent [12,13].…”

Use of ground-penetrating radar for water-table mapping, Brewster and Harwich, Massachusetts

“…Changes in moisture content, resulting from uneven recharge, variations in the type and density of material in the unsaturated zone, or both, change the value of the relative dielectric constant in the unsaturated zone significantly. For example, Jesch (1978), in laboratory tests using a 300-MHz signal, found that sand samples with an average density of 101 Ib/ft and moisture contents of 0,1,4, and 8 percent had average relative dielectric constants of 2.7, 3.2, 4.2, and 7.0, respectively. The relative dielectric constant is related to the signal propagation velocity by the equation--…”

Measuring the permittivity and permeability of lossy materials :

“…The loss factor at 18 GHz is modeled as e'; = 15.5m^, (239) where m^is the percent liquid water content; in these formulas m^ranges from to 16. • Soils have been measured by many researchers as functions of organic, sand, clay and water content [222][223][224][225][226][227][228][229][230][231][232] …”