Abstract
In order to clarify temperature dependence of unfrozen water film thickness and mechanism of the existence of unfrozen water in frozen soils, unfrozen water content was measured at various temperatures by the pulsed nuclear magnetic resonance technique. Soil samples used were Oya tuff in block and powder and Fujinomori clay with known specific surface areas. From the experimental results, the temperature (T) dependence of the unfrozen water film thickness (d) is obtained as d=d0 (Tm-T)-a, where Tm is the melting point of water (0°C). The values of d0 of these samples are between 8 and 12 nm, and the values of a are between 0.29 and 0.54. These experimental results were compared with the theoretical relationship in which the unfrozen water film thickness is dependent on the surface forces such as the Van der Waals force and the electric double layer force. The calculated film thickness decreased with decreasing temperature as shown in the experiments. However, the theoretical values are significantly smaller than the measured. The discrepancy of these values is considered to be due to structural component of the surface forces in the adsorbed water molecules on the mineral surface.
