Dielectric properties of frozen clay and silt soils

摘要

The dielectric properties of a clay and a silt soil have been studied at low water saturations at temperatures between −100°C and −15°C. The frequency range of the study (20 Hz–300 kHz) is lower than most other studies on permafrost. The results show a clear change in phase of the water in the soil at between −65°C and −80°C. The water can be modelled in terms of a thin layer of mobile molecules on the surfaces of soil particles. At low temperatures this layer has a non-Debye-like dielectric dispersion unlike that found for both water or ice. The relaxation frequency of the dispersion and its high activation energy are similar to those found for the quasi-liquid layer on ice particles. At temperatures above the phase transition, the dielectric dispersion is more Debye-like and indicates the presence of low frequency dispersion. We interpret this as due to a thin film of concentrated salt solution lining the soil particle pores giving rise to interfacial polarizations.