The Relationship Between Salt Concentration and Thermal Properties of Clayey Soils.

Clayey soils may be used as the most-outer barrier placed at the outside of containers with waste disposals in a geological disposal site. These waste disposals often contain salt solutions. In some cases,　the leakage of salt solutions may generate heat by hydration. To give a complete view of a barrier material, it is necessary to understand the effect of water content and salt solution concentration on soil thermal properties. The purpose of our research was to investigate salt-dependent thermal properties of clayey soils. A swelling montmorillonitic soil and a non-swelling kaolinitic soil were used. Solutions of NaCl, Na₂SO₄ and CaCl₂ were prepared with a concentration change between 0 and 1 mol/kg. Soil was mixed with the predetermined concentration of a salt for various solution contents of the soil. The mixed soil was packed in an acrylic column, and equilibrated to the room temperature (20℃). A three-wire thermo-time domain reflectometry (TDR) probe (0.040m long, 0.0075m spacing, Nichrome heater wire encased in the central rod and type T thermocouples in the rods of both ends) was used for measurements. Thermal properties were determined with a dual-probe heat-pulse technique. The results will be discussed.