Pore-Water Pressures in Freezing and Thawing Fine-Grained Soils

Laboratory freezing tests were performed on laterally confined samples of lightly overconsolidated fine-grained soil exposed to one-dimensional freezing at a constant temperature gradient. Pore-water pressures and temperatures were measured at the perimeter of the specimens at various points along their height during freezing and thawing. Vertical heave and water inflow and outflow were also recorded in the sample. X-ray pictures were taken in order to correlate ice lens formation to the measured data. Of particular interest were occurrences of high pore-water pressures shortly after the freezing front had stabilized. Pore-water pressure peaks coincided typically with temperature peaks. Maximum negative pore-water pressures measured during freezing can be correlated to the compression observed in soft clay specimens subsequent to freezing and thawing, which is often called freeze-thaw consolidation. During early freezing, no heave was indicated in soft clay specimens even though numerous ice lenses had formed. No freeze-thaw-consolidation was recorded for stiff clay specimens with initial water contents near the plastic limit.