ABSTRACT
Thermal properties of unsaturated soils have not been widely investigated, despite their wide range of engineering implications. The volumetric fraction of each component (air, water and soil) and the particle size distribution are key factors in determining the thermal properties of unsaturated soils. A Transient water Release and Imbibition Method (TRIM) was modified to integrate thermal properties measurements into the testing of the Soil Water Retention Curve (SWRC) and Hydraulic Conductivity Function (HCF). The TRIM system tests the water release under a two-step increase in matric suction and water imbibition under a one-step decrease in matric suction. The obtained transient water flow of drying and wetting is then processed as an objective function using inverse modeling to calculate the unsaturated hydrological parameters that define the SWRC and HCF of the soil. Moisture sensors and thermal needle probes were deployed in the TRIM system to capture the thermal property behavior during both drying and wetting. The constitutive relation between soil suction and water content in the SWRC reflects rich information of unsaturated soil: grain size and pore size distribution, relative density, and mineralogy, which in turn determine the thermal behavior of unsaturated soils. In this paper, the modified-TRIM test provides a fast, accurate, and simple way for obtaining thermal properties of unsaturated sands under both drying and wetting state, and correlates the thermal responses with intrinsic material properties of unsaturated sands.
