Estimating Thermal Conductivity of Pavement Granular Materials and Subgrade Soils

Abstract

The thermal conductivity of soils and granular materials is one of the most important parameters for frost action and thermal analyses in pavements and civil engineering infrastructures. Many predictive models were developed in past decades to correlate thermal conductivity of soils to basic soil index properties. Recently, relationships that cover the complete range of saturation in unfrozen and frozen states were established to consider the effects of porosity, geologic origin and mineralogy, soil type, particle type, and unfrozen water for a variety of soils. A simple and practical tool was developed to estimate thermal conductivity of pavement granular materials and subgrade soils directly as a function of the degree of saturation (water content) on the basis of these generalized thermal conductivity relationships. A new thermal conductivity equation is proposed to estimate thermal conductivity functions for soils such as well-graded gravels; coarse, medium, and fine sands; silty and clayey soils, and peat in unfrozen and frozen states. The new equation was successfully used to predict thermal conductivity functions of four different types of unfrozen and frozen soils from the literature (gravel, sand, clay, and peat). A set of charts is proposed to assess thermal conductivity of soils readily. The use of these charts is illustrated with examples. Both numerical and graphical estimating methods proved to provide accurate prediction results for thermal conductivities for soils and construction materials.