Factors Influencing Thermal Resistivity of Sands

Although many engineering projects require assessment of the thermal properties of soils for use in heat transfer calculations, geotechnical engineers are often unfamiliar with procedures for measuring these properties. A simple test for measuring the thermal properties of soils, called the “thermal needle” test is described. The apparatus and procedure have been refined to allow measurement of the thermal resistivity of sands for conditions of elevated temperature, water content reduction by stage, drying, and long‐term saturation. Laboratory thermal needle tests were conducted using surge sand, silica sand, and Monterey 60 Sand; it was found that the thermal resistivity decreased with increasing temperature and increasing compaction water content. Also, the thermal resistivity of silica sand decreased with time of saturation. The test results are not only useful for study of thermal geotechnical problems, but could be used to interpret other structural and mechanical property characteristics of sands.