A generalized thermal conductivity model of soil-rock mixture based on freezing characteristic curve

Soil-rock mixtures, served as important geotechnical materials for road construction and embankment dams, are widely distributed in cold regions. Thermal conductivity is a significant parameter in qualitatively assessing the heat transfer properties and determining the temperature field in cold regions geotechnical engineering. This study experimentally investigated the influence of rock content and temperature variations on the thermal conductivity of soil-rock mixtures, and a generalized thermal conductivity model based on the freezing characteristic curve was established. The results showed that both rock content and water-ice phase transitions affect the heat flux within soil-rock mixtures. The heat flux exhibited distinct variation trends during the freezing-thawing processes. Notably, hysteresis in heat flux was observed during the early stages of freeze-thaw cycles, disappearing after 8, 6, and 4 freeze-thaw cycles for soil-rock mixtures with rock contents of 10 %, 25 %, and 40 %, respectively. Additionally, the rock content seldom influenced the freezing temperature, while it significantly affected the thermal conductivity of soil-rock mixture. Furthermore, a generalized thermal conductivity model based on the freezing characteristic curve was established and verified, the proportion of thermal conductivity associated with the water-ice phase increased for the modified parallel model, while the modified series thermal conductivity model exhibited reversed results as the temperature decreased. Moreover, all the thermal conductivity models could obviously reflect the water-ice phase transition on the thermal conductivity of soil-rock mixture. However, the modified effective thermal conductivity model agreed best with the experimented results.