Soil-Water Potential and Unfrozen Water Content and Temperature
Xu Xiaozu (Lanzhou Institute of Glaciology and Geocryology, Academia Sinica) J. L. Oliphant and A. R. Tice ( U. S. Army Cold Regions Research and Engineering Laboratory)
Soil-water potential was determined by the extraction method and four factors affecting the soil-water potential, including water content, soil type, dry density and temperature, were investigated. The unfrozen water content of frozen soils was determined by the pulsed nuclear magnetic resonance technique and three factors affecting the unfrozen water content, including initial water content, dry density and salt concentration, were investigated. Results have shown that the soil-water potential in the unsaturated, unfrozen soils decreases both with the decrease in the water content and with the increase in the dispersion of the soil and increases with the increases in the dry density and temperature. The unfrozen water content of frozen soils changes slightly with the initial water content and the dry density within the range of 3% for the morin clay and increases sharply with the increase in the salt concentration. There is a good linear relationship between the unfrozen water content and the molality.It was found that the relationships between the soil-water potential and the water content, between the unfrozen water content and temperature and between the soil-water potential and temperature in frozen soils may be expressed in the power law form. Prediction of the unfrozen water content could be made by the measurements of the initial water content and its freezing point (two-point method) or by the measurement of the unfrozen water content only at the temperature of minus one degree centigrade (one-point) method. Errors between the observed and the predicted data for the two methods are, within the range of 3%.