Abstract
Hysteresis phenomena in the thermal conductivity of frozen soils between freezing and thawing processes were investigated and discussed from a view point of the amount of unfrozen water contained in the frozen soils. Thermal conductivities of frozen alluvial and ando soils have shown hysteresis and these were higher in the thawing process than in the freezing one. The same soils also showed the hysteresis in the amount of unfrozen water which were less in the thawing process than in the freezing one. The differences of the thermal conductivity and the amount of unfrozen water between the two processes became larger with the increase of initial soil water content at freezing, and the differences of the values at-2°C were larger than at-6°C. However, the sand soil have not shown the hysteresis in the thermal conductivity and the amount of unfrozen water between the two processes. It is revealed that the hysteresis of the thermal conductivity was due to the fact that the thermal conductivity of ice was four times larger than unfrozen water and the thawing process contained less unfrozen water or more ice than the freezing process at the same temperature.
