This column is provided as a public service by the Geophysical Institute, University of Alaska Fairbanks, in cooperation with the UAF research community. T. Neil Davis is a seismologist at the institute. Freezing soil can create such great upward forces on telephone poles, bridge pilings and similar objects that they are literally lifted out of the ground.
Several factors control the amount of frost heaving and the consequent lifting force on a piling.
The expansion is not caused only by the freezing of the water contained in the soil but also by the freezing of new water that migrates upward from below the frost line during and after the freezing of the soil. The colder the ground surface, the greater is the transport of water upward. Freezing of this new water can create layers of pure ice within the top layers of the soil, even after the soil has become frozen. Consequently, frost heaving can continue right on through the winter if there is an adequate supply of water from below. Russian experiments have shown that some clays, as they freeze, can nearly double in volume, especially if saturated with water rich in aluminum, iron or calcium.