Study on soil thermal conductivity draws much attention recently since it is a governing soil thermal property in heat transfer process for geothermal applications. The variation of soil thermal conductivity at shallow depth is less understood because it is affected by various environmental factors (e.g. temperature, humidity, precipitation, etc.). This paper presents the measurement of thermal conductivity dry-out curves (TCDCs) for sands using a modified hanging column device (MHCD). Thermal conductivity of three sands was measured continuously from fully saturated condition to dry condition using a KD2 Pro (i.e. TR-1 single probe). A thermo-TDR probe was also used to measure sand moisture content. TCDCs of test sands were established with respect to degree of saturation, and then compared with the measured thermal conductivities obtained by multiple-specimen method (MSM). A good agreement of measured thermal conductivity was found between the MHCD and the MSM. The predicted TCDCs by three alternative thermal conductivity models were also compared with the measured curves. Recommendations have been provided to improve the models for wider applications.
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