Correlation of Thermal Conductivity and Electrical Resistivity of Soil – For Near Surface Geothermal Applications

Abstract

SUMMARY Soil thermal conductivity (k) is a critical parameter in various engineering applications, where heat transfer takes place and depends on numerous factors such as mineralogical composition, grain size of soil and physical properties (moisture, dry density, saturation). Same factors have also an influence on the electrical resistivity of soil (ρ). This work presents an experimental determination of soil thermal conductivity and electrical resistivity, in various soil types with different grain size and mineral composition, in terms of variable moisture content and dry density. The change of thermal (k) and electrical (inverse of resistivity, ρ) conductivity values in terms of the increasing saturation is interpreted with the increasing presence of water over the air in the pore space that facilitates heat and current transportation. The study of thermal conductivity and electrical resistivity variation according to the fluctuation of physical properties of soils, can lead to the qualitatively and quantitatively correlation between kand ρ. Such an empirical correlation can be used to estimate the thermal conductivity of subsurface, by applying electrical resistivity tomography in combination with geotechnical data. At the present time, it is a subject of further research exploiting various models of k and ρ.