Three Laboratory Methods for Measuring Thermal Resistivity Dryout Curves of Coarse-Grained Soils

摘要

Thermal resistivity dryout curves (TRDCs) are measured for twelve sandy soils representing a range of grain characteristics and grain size distribution. Experiments are conducted using three laboratory methods for comparison: (ⅰ) an instrumented hanging column apparatus for concurrent measurement of the TRDC and soil-water characteristic curve (SWCC) during drainage, (ⅱ) a staged-drying method involving a single specimen subject to discrete drying increments in a 50℃ oven, and (ⅲ) a multiple-specimen method involving compaction of multiple specimens prepared at different water contents for independent thermal resistivity measurements. TRDCs obtained using the three methods were comparable (within ～10 %). The instrumented hanging column method produces the most robust TRDCs, but potentially overestimates thermal resistivity at relatively high saturations. The staged-drying method may produce slightly lower resistivity due to elevated soil temperature at the time of the measurement. The multiple-specimen and staged-drying methods potentially overestimate thermal resistivity at low saturation due to contact resistance and sample disturbance resulting from probe insertion and removal. TRDCs using the multiple-specimen, staged-drying, and hanging column method were obtained in about 1 day, 10 days, and 23 days, respectively.