Abstract
<title>Abstract</title> <p>Frost heave is a major cause of pavement damage in cold regions, where the growth of ice lenses in frost-susceptible subgrade produce differential ground movement, deformation, and cracking. This study presents a transient coupled temperature-displacement finite-element model for predicting frost heave and its structural effects in layered flexible pavements. Latent heat released during pore-water freezing is represented using the apparent heat-capacity method, and frost heave is simulated through a temperature-dependent expansion model based on the free-heave strain of the soil. Calibrated with a free-heave strain of 1% for a frost-susceptible silt, the model predicted a surface heave of 14.3 mm, within 3% of the literature value of 14.7 mm. The predicted heave and peak tensile stress (2.76 MPa) were correctly concentrated above the frost-susceptible zone, and a sensitivity analysis confirmed an almost perfectly linear relationship between free-heave strain and surface heave (R² = 0.9998). The validated model was then applied to evaluate three widely used frost-mitigation strategies. A 76 mm insulation board was the most effective, reducing surface heave by about 99% and almost eliminating frost-induced tensile stress, with negligible differences between polystyrene, polyurethane, and glass-fibre boards. Lime stabilisation of the upper 0.30 m of the subgrade reduced surface heave by 73% and peak tensile stress by 77%, while subgrade drainage, represented by a reduced degree of saturation, achieved heave reductions of 20% and 41% at 80% and 60% saturation, respectively. The proposed framework provides a practical and computationally efficient tool for evaluating frost-mitigation measures and supporting the design of durable flexible pavements in cold regions.</p>