Thermal Conductivity of Quartz Sands by Thermo-Time Domain Reflectometry Probe and Model Prediction

The heat transfer process in soil depends on its thermal conductivity property and is affected by soil compositional and environmental factors, such as soil gradation, mineralogy components, compaction moisture content, and dry unit weight conditions. In this research, thermal conductivities of three quartz sands were studied using a newly developed thermo-time domain reflectometry (TDR) probe. The test results revealed that thermal conductivity of quartz sands increased with compaction moisture content and dry unit weight. Higher quartz content also led to higher thermal conductivity. The new thermo-TDR probe provided measurements of thermal properties similar to those of the standard KD2 probe. The deviation of the two methods was within 5%. An improved thermal conductivity model was also proposed on the basis of the normalized thermal conductivity concept and present experimental data. This improved model exhibited the highest accuracy in thermal conductivity predictions of quartz sands (within 15% deviation at all soil moisture conditions). The R-2 value, lowest standard error from linear regression analysis, and relatively low root-mean square error (RMSE) analysis value was compared with those of five other thermal conductivity models. The results indicated that the proposed model provided very good predictions. (C) 2015 American Society of Civil Engineers.