This study investigates the impact of moisture redistribution during the measurement of the thermal dry-out curve (i.e., soil thermal resistivity, ρ_T, versus moisture content, θ). Thermal dry-out curves are used in energy geotechnics (e.g., geothermal heating and cooling, collector systems at wind energy sites) to quantify the capacity of a soil to store or dissipate heat. Although there is not a standard method for measurement of the ρ_T-θ relationship, curves are typically generated by measuring ρ_T of remolded or undisturbed specimens at varying water contents, typically with incremental measurements as the specimen is dried. However, drying within a specimen may not be uniform, even in a controlled, low-temperature, drying environment. In this study, a thermal properties probe was used to measure ρτ of remolded cylindrical specimens as the soil was dried in a low-temperature oven. Three horizontal sensor locations (top, middle, and bottom) were used to measure px across the specimen. Water content at the sensor locations was measured and compared to the corresponding ρτ measurement. Thermal resistivity tests were performed at various drying times for three soils: Poorly Graded Sand (SP), Silty Sand (SM), and Sand with Silt (SP-SM). Tests on SM remolded at 95% maximum dry density revealed θ up to nine times higher in the bottom sensor location than in the top sensor location. The test results indicate a need for modification of the standard thermal resistivity testing procedure such that moisture migration within a specimen during drying does not impact the testing accuracy.
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