Volume 1, Issue 3 (September 1978)
Dielectric Constant Determination of Soils at L Band Microwave Frequencies
The use of microwaves as a nondestructive testing method for penetrating the ground and detecting subsurface details and anomalies is currently receiving active consideration. All variations of the technique require knowledge of the dielectric constant of the soil being penetrated by the microwaves. This paper presents a method for determining the dielectric constant of soils under various density and moisture conditions at L band frequencies, namely, 0.39 to 1.5 GHz. Using a technique based on open wire transmission line theory it was found that: 1. Dielectric constant decreases linearly as porosity increases. 2. Dielectric constant increases rapidly as moisture content increases. 3. Dielectric constant is soil type-dependent. 4. Microwave properties in soils are conveniently related to volumetric water content, a term which includes both porosity and water content characteristics. 5. Temperatures above freezing have little effect on dielectric constant. 6. The open wire transmission line test is convenient, rapid, and easy to perform for remolded soils in the laboratory.