Abstract:

The thermal conductivity of soils is a key parameter in analysis of soil heat transfer in geotechnical engineering. This paper intends to develop a generalized thermal conductivity model for unsaturated unfrozen and frozen soils based on the concept of normalized thermal conductivity with respect to dry and saturated states of soils. 328 groups of experimental results for unfrozen and frozen soils, such as gravels, sands, silts, clays and peat, available from the literature were analyzed to develop the general relationship between the normalized thermal conductivity of soils and the degree of saturation. A unique normalized thermal conductivity and degree of saturation (normalized water content) relationship is obtained for the soils with different porosity and different thermal conductivity and water content relationships. There is a strong linear relationship between the inverse of normalized thermal conductivity (1/kr) and the inverse of degree of saturation (1/Sr) with lines passing through the coordinate (1,1). The soil types control the slope of the 1/kr-1/Sr lines. Accordingly, the model integrating the effects of soil types, density (or porosity) and water content (or degree of saturation) on the thermal conductivity of unfrozen and frozen soils is proposed. Method and parameters for calculating the thermal conductivity of dry and unfrozen or frozen saturated soils are given. The model generally predicts the thermal conductivity within an error of 20% for all kinds of (unfrozen and frozen) soils studied.

Key words: heat transfer, thermal conductivity, soil, frozen soil, degree of saturation