Evaluating soil thermal conductivity for buried infrastructure: Impact of water salinity, mineral composition, and moisture content on heat transfer

Thermal conductivity of soils is a critical soil property in geotechnics, which provides essential information about the soil's ability to conduct heat transfer. Erroneous data can be responsible for the inefficient design of buried infrastructure systems that rely on heat transfer, such as buried cables, piping, and geothermal systems. There is a lack of fundamental knowledge on the soil thermal conductivity under in-situ conditions factoring soil type, alteration in moisture content, and salinity. Our research aims to address how groundwater, flooding, or drought can impact thermal conductivity due to moderate-to-high soil salinity levels; as these may be critical factors to be considered in soil thermal conductivity testing for infrastructure. This study investigated the influence of salinity concentrations on soil thermal conductivity, with potential implications for areas with a high water table, rainfall, or flooding events, as well as offshore wind projects. This study accounted for variations in soil type and water salinity concentrations when testing for the thermal conductivity of soil. Twenty-three (23) experimental tests were conducted with a resulting 36 thermal conductivity data points recorded. The results were further analyzed in comparison with data results obtained from using the current industry-accepted methodology, which does not account for varying salinity concentrations. The results suggest that sand soil was most conductive when added with 15 g/L brine. Further, the salinity concentration or soil type can increase (silty clay) or decrease (sandy soil) soil thermal conductivity at varying moisture contents, which could provide a more informed, economical design for buried infrastructure that relies on heat transfer through soils.