|Mcintosh, Gordon - UNIVERSITY OF MINNESOTA|
Submitted to: Seasonally Frozen Soils Symposium
Publication Type: Proceedings
Publication Acceptance Date: June 12, 1997
Publication Date: N/A
Interpretive Summary: Determining the time of occurrence and depth of soil freezing are useful in assessing runoff from fields, the depth at which city pipes should be buried, and the potential for flooding in northern regions. Computer programs are available that attempt to predict whether soils are frozen. Frozen soils can also be assessed using the standard frost tube, an instrument requiring human intervention. The electrical potential of soil changes as ice replaces water in the porous structure of soils. An automated instrument that continuously monitors the electrical potential of soils without human intervention was developed and used to assess whether soils were frozen. Conservationists, meteorologists, hydrologists, and engineers may be able to utilize this instrument to assess in real-time whether soils are frozen. Real-time information on soil freezing will allow action agencies such as the National Weather Service to better forecast the potential for flooding of major rivers.
Technical Abstract: Freezing modifies various electrical properties of soils. The electrical modifications, changes in conductivity (resistance) and dielectric constant and the generation of a small potential difference across the frozen - unfrozen interface, can be used to determine the location of the freeze front through automated techniques. We conducted a laboratory experiment to investigate the change in resistance as the soil freezes and to use this change to monitor the location of the freeze front. We found that the slope of the resistance versus time curve changed distinctly at the depth of 0 deg C isotherm, and the change accurately indicated the depth of frost.