Thermal Conductivity of Granular Soil Mixtures with Contrasting Particle Shapes

Particle shape is known to affect the mechanical behavior of sands because it influences packing density and particle contacts. Even though the thermal conductivity of sands also depends on packing density and particle contacts, the effects of particle shape on thermal conductivity are not well understood. A series of thermal needle tests were conducted on five granular soil mixtures with different proportions of rounded and angular glass particles having the same mineral composition and gradation. The maximum and minimum void ratios and the packing density of these mixtures were found to depend on the overall regularity, defined as the average value of the particle's aspect ratio, convexity, and sphericity. For a given overall regularity, the thermal conductivity increases with decreasing void ratio or increasing relative density. Interestingly, the overall regularity has a small effect on the thermal conductivity at a given void ratio but has a significant effect on the thermal conductivity at a given relative density. A particle shape-dependent empirical equation is proposed to quantify the effects of relative density and overall regularity on the thermal conductivity of the tested sand.