Stress distribution in frost heaving soils

Studies in recent years have established that growth of ice lenses in freezing soils is not limited to the boundary between the frozen and unfrozen soil but continues within the already-frozen material. Consequently, the enlargement of such lenses must take place against the resistance offered by the surrounding semi-rigid frozen soil. The upper limit of pressure which can be asserted by the growing lens is thermodynamically determined by its temperature and, in accordance with the Clausius-Clapeyron equation, the potential of the water available for the lens. If the lens is able to grow it will do so at a rate which is a complex function of the long-term creep of the surrounding soil. A prolonged series of experiments has been carried out involving the use of very small pressure transducers to record pressures developed within frost heaving soils as a function of temperature. The values obtained can be explained in accordance with these concepts. The externally-effective heaving pressure of the frozen soil depends on the pressure in the ice lens as determined by the temperature and water potential in the Clausius- Clapeyron equation, less the resistance offered by the intervening layer of frozen soil.