The thermal properties of soils are of great importance in many thermo-active ground structures such as energy piles and borehole heat exchangers. In this paper the effect of the porosity and degree of saturation on the thermal conductivity of a sandy soil that has not been previously thermally tested is investigated using steady state experimental tests. The steady state apparatus used in these tests was designed to provide high performance in controlling all boundary conditions. Twenty thermal conductivity experimental tests have been carried out at different porosity and saturation values. The performance of selected prediction methods have been validated against the experimental results. The validation shows that none of the selected models can be used effectively in predicting the thermal conductivity of Tripoli sand at all porosity and saturation values. However, some can provide good agreement at dry or nearly dry condition while others perform well at high saturations. The performance of most of the selected models also increases as the soil approaches a two phase state where conduction plays the dominant role in controlling heat transfer. An empirical equation of thermal conductivity expressed as a function of water content and porosity has been developed based on the experimental results obtained
