Gradation-Dependent Thermal Conductivity of Sands

Abstract

Although thermal conductivity is a widely applied parameter in geotechnical engineering, the effect of soil gradation on the thermal conductivity is not well understood. Thermal needle tests were performed to analyze the influence of gradation on the thermal conductivity of carbonate sands. The thermal conductivity of carbonate sand specimens having different gradations prepared to three void ratios was observed to increase with uniformity coefficient or fractal dimension. Although an increase in void ratio leads to a decrease in thermal conductivity, the percent difference in thermal conductivity is independent of the initial void ratio. A maximum increase in thermal conductivity of 13.9% was observed for uniformity coefficients ranging from 2 to 2. Empirical equations using the uniformity coefficient are proposed to quantify the gradation-dependent thermal conductivity of carbonate sand for use in the design of insulating layers.