Determination of Effective Thermal Conductivity for Tripoli Sand as Influenced by Changing Water Content and Density

Abstract

The thermal properties of soils are of great importance in many thermo-active ground structures such as energy piles, borehole heat exchangers and underground power cables. The steady state apparatus used in the determination of the thermal properties of soils, were designed to provide high performance in controlling all boundary conditions. In this study thermal cell apparatus was chosen due to its simplicity and because it is inexpensive and does not require a large quantity of sample. This study was conducted to determine the effect of moisture content and density of the soil on the effective thermal conductivity of Tripoli sand, through a series of laboratory experiments, at different porosity and saturation values. For specimens with low moisture contents, the results showed a nonlinear increase in the effective thermal conductivity, while for soils with high moisture contents, the thermal conductivity was observed to have linearly increased. The maximum value for the effective thermal conductivity was obtained at the maximum dry density at the saturation state. In contrast, the minimum value was at the minimum dry density at the dry state