Frost-depth penetration and frost heave in frost-susceptible soils

The natural freezing and thawing of soils dramatically affects their thermal and mechanical properties.This can have destructive effects on structures built on those soils.This study developed a thermodynamic finite element model using multiple frost-susceptible soil types.It measured thermal conductivity and temperature through several freeze-thaw cycles.We identified moisture migration as likely the most significant factor in frost heave and frost penetration.Additionally, the thermal conductivity increased near the freezing front across all samples.For example, the thermal conductivity for ML (low-plasticity silt) soils rose from 301 to 357 milliBtu/(hr*ft*°F), which appeared to correspond to where the moisture concentrated and ice formation was highest.Our experimental results guided model development, where thermal parameters changed with respect to temperature, ice, and moisture during freeze-thaw cycles.Using dynamic thermal parameters improved frostdepth prediction compared to the standard Modified Berggren equation.For our tested conditions, the equation had an error of 2.2 in.for a frost depth of 8 in.while our model had an error of 1.4 in.These developments are important to airfield runway and general pavements design and maintenance in frost-affected regions.The findings will allow more accurate predictions of frost depth and deflection.