Soil Moisture Variations in Frozen Ground Subjected to Hydronic Heating

Abstract

Full-scale thawing experiments, performed on three types of homogenous, initially frozen soils, were carried out during late winter 2011 and repeated in 2012. An auxiliary heat source (hydronic heating) was employed to initiate and expedite the thawing process. The corresponding phase change, soil temperature increase, and variations in bound and unbound water content were monitored during the experiments. The resulting thermal response have been published in an earlier paper by the authors. In the current paper, the remaining results are presented. This includes spatial and temporal soil moisture variations and resulting thaw rates. Results from both experiments show similar trends. Generally, frost-susceptible soils, such as silty sand, contain more water and thaw slower relative to coarser soils, such as gravelly sand. Very porous soils (uniform gravel) with low water content thaw comparatively slower. Thaw rates compiled from soil moisture records correspond well with similar based on soil temperature. The degree of water redistribution and migration is higher in silty sand compared with coarser soils. These processes are more prominent in the uppermost layer for all soils examined.