Thermal conduction behaviors of dry sands considering effects of particle shape

The aim of this study is to reveal the influences of particle shape of dry sands on their thermal conductivity. A series of particle shape determination and thermal probe experiments are conducted to investigate the statistical distribution characteristics of two-dimensional particle morphology for various natural river sands and the relationship between particle shape parameters and thermal conductivity. The internal mechanisms of contact thermal conduction among sand particles are also discussed in mesoscale. The results indicate that both the roundness and the sphericity of natural sand exhibit normal distribution features in statistics, and their expected values are the proper parameters for quantitatively characterizing the particle morphology. The thermal conductivity displays a linearly decreasing trend with an increasing porosity in the semi-logarithmic coordinates, with the slope of the line linearly decreasing with the increase of the average shape factor A_m. At a given porosity, round particles possess higher thermal conductivity, and the higher porosity leads to the less significant discrepancy in the thermal conductivity of different dry sands. The proposed model is excellent in applicability and advanced as compared to the Côté and Konrad model. The effects of particle shape on the thermal conductivity for dry and non-cohesive soils are comprehensively affected by multiple factors, which are dependent on the factors including stress condition and particle stiffness.