Estimating the Dielectric Spectrum of Unsaturated Soils with Different Moisture Contents

To establish a method for evaluating the dielectric spectra of unsaturated soils, spectra of the real permittivity of Toyoura standard sands ( sand f l ) with different volumetric water contents ( i ) were determined by employing a vector network analyzer. Their results were verified based on a comparison with the theoretical values calculated using a modified dielectric mixing model. The spectra of above 0.23 m 3 m -3 could not be estimated owing to unreproducible soil packing. However, suitable spectra that approximately agreed with the theoretical spectra, were successfully estimated when i was less than 0.19 m 3 m -3 . Although further modifications of the foregoing approaches are required to obtain more reliable spectra of sand f l for Toyoura standard sands with high moisture contents, the proposed methods can aid in evaluating the spectra of unsaturated sands with low or moderate volumetric water contents.