Canadian Field Soils III. Thermal-Conductivity Data and Modeling

Forty field soil samples, from nine Canadian Provinces, were laboratory tested for their ability to conduct heat, i.e., thermal conductivity (), using a non-stationary probe technique. The measurements were carried out on moderately compacted samples at room temperature, and over a full range of degree of saturation ( ranging from dryness to full saturation. The analysis of data revealed a strong nonlinear variation of versus that can be sub-analyzed in four -based domains, i.e., residual, transitory meniscus, micro/macro-porous capillary, and superfluous. In the residual domain (, a very small variation is observed. In the transitory meniscus domain (, for the majority of soils, a sharp increase was observed. In the micro/macro-porous capillary domain (, a moderate increase was noted. Finally, in the superfluous domain (, a very slight increase was generally noted. On average, the highest values (from 1.9 to 3.2 were obtained from saturated soil samples with high quartz content, e.g., samples from sites in Nova Scotia and Prince Edward Island. On the other hand, the lowest (from 1.1 to 1.4 was observed from saturated soil samples with lower quartz content, e.g., British Columbia samples. The measured data were used to verify a recently developed series-parallel (S-) model for unsaturated soils. On average, estimates of the S- model, with a parallel arrangement of air and water in the third of three conductive paths, were within of experimental data. However, the S- model, with a series arrangement of air and water in the third conductive path, showed slightly better estimates when it was applied to fine-textured soils. In addition, there was no strong correlation noted between the performance of the S- models and soil quartz content. Consequently, it is recommended to compare estimates from both models when they are applied to experimental data.