|Mcintosh, Gordon - UNIVERSITY OF MINNESOTA|
Submitted to: Cold Regions Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 30, 1997
Publication Date: N/A
Interpretive Summary: Municipalities need information concerning frost depth in developing criteria on how deep pipes must be buried to avoid freezing. The National Weather Service also needs real-time information on soil frost to improve their capabilities to predict river flooding. Since no technology exists for monitoring frost depth on a continuous basis, we carried out several experiments to determine frost depth by measuring changes in the electrical resistance of soils. The electrical resistance of soil changed abruptly as the soil froze with the rate of change being dependent on soil water content. Continuously measuring changes in electrical resistance of soils now offers engineers an inexpensive and quick method to monitor frost depth.
Technical Abstract: Soil freezing and thawing have important implications to the stability of aggregates as well as manmade structures whose foundations lie above the depth of seasonal frost. Frost depth also determines the depth to which pipes are buried and animals burrow to avoid subfreezing temperatures. We have carried out several experiments in determining frost depth by measuring changes in the electrical resistance of soil. Changes in the electrical resistance were determined under the conditions of an advancing and retreating frost front in a loam at water contents of 25 and 35% by volume. The resistance determination was compared to other techniques for determining the frost depth in soil. The electrical resistance was not a simple function of soil temperature nor of the state of pore water as previously reported. Under certain conditions, the resistance decreases as the temperature decreases converse to naive expectations. Our results suggest that electrical resistance can be used to ascertain frost depth as this technique coincided with the advance and retreat of the 0 deg isotherm.