Frost heaving
From Biocrawler, the free encyclopedia.
Frost heaving (or frost heave) occurs when soil expands upward or outward and contracts due to freezing and thawing. This process can damage plant roots through breaking or desiccation, cause cracks in pavement, and damage the foundations of buildings, even below the frost line. Dry, moist soil at certain temperatures is most susceptible to frost heaving.
Cause
Originally, frost heaving was thought to occur due simply to the freezing of water in soil. However, the vertical displacement of soil in frost heaving can be significantly greater than the expansion that occurs when ice freezes. In the 1960s, frost heaving was demonstrated in soil saturated in benzene and nitrobenzene, which contract when they freeze.
The current understanding is that ice crystals forming in soil draw water from the surrounding soil, in a process similar to drying. Heat caused by the freezing process prevents lower levels of soil from freezing as well. Depending on the amount of moisture available, a significant amount of soil displacement can result.
The earliest known documentation of frost heaving came in the 1600s.
See also
External links
- Canadian Building Digest article (http://irc.nrc-cnrc.gc.ca/cbd/cbd026e.html)
- The Mechanisms and Effects of Frost Heave (http://www.acad.carleton.edu/curricular/GEOL/classes/geo258/studentswork/McGee.html)
- American Institute of Physics pictures of frost heaving (http://www.aip.org/png/html/frost.htm)
