Development of a frozen soil dielectric constant model and determination of dielectric constant variation during the soil freezing process

We used an interaction model of electromagnetic waves and mixed dielectric in unsaturated soil to develop an electromagnetic wave and mixed dielectric model of frozen soil. The new dielectric constant model was used to investigate the effects of temperature, mass water content (θm), and dry density on the relative dielectric constant (εr) of a yellow clay soil in Harbin, China. Based on frequency domain reflectometry (FDR) sensors under field conditions, the influencing factors were altered during measurements and the corresponding changes in soil εr were recorded for comparison and analysis. The influence of temperature on εr occurs mainly during the phase change period of liquid water in soil, while in the positive temperature range, εr varies only slightly with temperature. The εr increased with θm or dry density when the temperature was above 0 °C, but εr varied little with respect to θm or dry density after the soil froze. The accuracy of the proposed dielectric constant model in frozen soil was validated by comparing actual and predicted εr values.