A case study of potential causes of frost heave

Abstract : Frost action beneath pavements can lead to several problems, including thaw weakening, which causes cracking and subsequent pumping of fine soil particles onto the surface, as well as hazardous conditions caused by differential heaving. This study examined data and frost-susceptible soil collected during the winter of 1985-86 at Ravalli County Airport, Hamilton, Montana, to determine potential causes of frost heave. Variables analyzed were depth to water table, depth of frost penetration, maximum frost heave and soil moisture tension and soil temperature with depth. Analysis of the field data revealed the possibility that hydraulic conductivity of subgrade soils and rates of heat loss in the soil may be limiting frost heave rates. Soil density and depth to water table may also be factors affecting amounts of frost heave. Furthermore, the base course 'gravel' used at the airport contained considerable amounts of fines and did heave somewhat in laboratory tests. Recommendations for design changes to reduce frost heave at Ravalli County Airport were made. (edc)