Relevance of capillarity to thermal and electrical conductivity in unsaturated granular soils

Capillarity critically determines the air-entry value, which in turn influences the pressure-dependent water retention capacity in unsaturated soils. Current engineering practice, however, mostly focuses on wettable soils although nonwettable soils often exist due to casual and natural events. This study presents the experimental investigations of soil-water characteristic curves (SWCC) for both hydrophilic (wettable) and hydrophobic (nonwettable) soils in conjunction with the measurement of thermal and electrical conductivity. Natural sands are artificially treated to impose the nonwettability using organo-silane. The surface wettability effect on conduction phenomena and matric suction is emphasized. Results show a nominal difference in air-entry pressure for hydrophilic and hydrophobic sands and the conductivity values are quite close to each other. This may be attributed to the relative particle void size in sands.