Effect of Hydro-mechanical Changes on the Relationship between Thermal Conductivity and Dielectric Permittivity of Soils

Soil thermal properties such as thermal conductivity and resistivity, thermal diffusivity and specific heat capacity are vital in conducting analysis and modeling in various fields of geo-mechanics, agriculture, hydrology and others. Heat and water transfer problems in geo-mechanics are strongly coupled processes, thus producing transient temperature, moisture content, stress and thermal conductivity variations in unsaturated soil conditions. Understanding of this coupled phenomenon requires the accurate estimation of thermal conductivity of soil at different soil hydro-mechanical conditions. The same factors affecting soil thermal conductivity also play a predominant role in soil dielectric permittivity or conductivity, and its variations with hydro-mechanical changes (De Vries, 1963; Tarnawski, 2000; Archie, 1942). In this study, the variation of thermal conductivity and dielectric permittivity of three silty clay soils with applied effective stress under one dimensional loading was theoretically studied. Johansen’s (1975) model of soil thermal conductivity and the advanced Lichtenecker and Rother Model (ALRM) (Wagner et al., 2011) of soil dielectric permittivity were both modified using correlations of soil compressibility suggested by Nishida (1956), to analyze the thermal conductivity and dielectric permittivity of the soils at different hydro-mechanical conditions.