Measurement of Thermal Conductivity Function of Unsaturated Soil Using a Transient Water Release and Imbibition Method

Abstract

**Please note that the full text is embargoed** ABSTRACT: Thermal conductivity of unsaturated soil depends on soil water content and soil type. A transient water release and imbibition method (TRIM) is modified to include measurement of the thermal conductivity function (TCF) in conjunction with concurrent measurement of the soil water retention curve (SWRC) and hydraulic conductivity function (HCF). Two pairs of dielectric and thermal needle sensors are embedded in the soil specimen to monitor spatial and temporal variation of water content, thermal conductivity, and thermal diffusivity during drying and wetting processes. Three different soils, including pure sand, silt, and clayey sand are used to examine the effectiveness and validity of the new technique. The thermal conductivity data from the modified TRIM technique accords well with other independent measurements. The results show that the modified TRIM technique provides a fast and accurate way of obtaining thermal properties of different types of soils under both drying and wetting states. The typical testing time for a soil going through a full saturation variation is less than 3 weeks. We observe that the hysteresis in thermal conductivity during a wetting and drying cycle is much less pronounced than that of the hydraulic hysteresis. [Copyright by ASTM Int'l. This is a published version of an article published in Geotechnical Testing Journal (GTJ) on September 19, 2014, available online: https://compass.astm.org/DIGITAL_LIBRARY/JOURNALS/GEOTECH/PAGES/GTJ20140046.htm, DOI: 10.1520/GTJ20140046].