Heat Transfer and Frost/Thaw Penetration in Soil Surrounding an Inclusion of Sand: Numerical Model Results Relevant to Electromagnetic Sensor System Performance,
Abstract
One- and two-dimensional numerical simulations of heat flow in silty soil with and without a sand inclusion (15 cm thick, variable width) have determined the magnitude and the lateral extent of the disruption in frost and thaw penetration attributable to the presence of the inclusion. Four different soil temperature histories, derived from field data at a Vermont site, were used as the surface boundary condition for the winter-long simulations. This identified differences in frost depth and soil temperature resulting solely from an overall colder or warmer soil surface condition. For a given surface boundary condition, the moisture content of the soil was varied (10, 17 or 25%, by weight) to contrast the changes in frost penetration caused by the moisture-dependent differences in soil thermal conductivity and latent heat. The drier sand (3% moisture content by weight) with its smaller latent heat freezes more rapidly than does the soil under identical conditions, so initially (early winter) frost penetration is greater (by 5% cm) when the sand inclusion is present because the freezing front proceeds rapidly through the sand. Subsequently, the freezing front is deeper (by a maximum of 11 cm) in soil without a sand inclusion. The less conductive sand impedes heat flow toward the soil surface, resulting in higher soil temperatures beneath the inclusion, which in turn retards freezing of the soil. Frost penetration beneath a sand inclusion is deeper the drier the soil is; with no sand inclusion present, frost depth is greater the more moist the silty soil is. Under the conditions of this study, maximum frost penetration is 61 cm ("coldest" surface boundary condition, 25% moisture content soil, no sand inclusion).
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1995
- Accession Number
- ADA299439
Entities
People
- Kevin O’neill
- Lindamae Peck
Organizations
- Cold Regions Research and Engineering Laboratory