An Analytical Approach for Predicting Vapor Migration Induced by Pot Cover Effect With Field Test Validation

ABSTRACT Pot Cover effect describes a process in which vapor migrates upward along a temperature gradient, condenses and accumulates as liquid water or ice at the base of a covering impermeable layer, ultimately resulting in pavement damage. Although numerical simulation, analytical calculation and empirical models are widely used to calculate vapor migration caused by Pot Cover effect, there are limitations in their computational efficiency under specific conditions. To overcome this limitation, an analytical approach based on Fick's law and fundamental physical assumptions is developed to quantitatively describe vapor migration. Validation using field test data from Beijing Daxing International Airport confirms the accuracy of this approach in capturing vapor migration in freezing unsaturated soils. Furthermore, the analytical approach is applied to investigate the influence of the separation layer's depth and gas permeability on vapor migration. The optimal configuration is identified as a layer positioned at the maximum freezing depth (40 cm in this study) with nearly 0% gas permeability, which most effectively inhibits vapor migration induced by Pot Cover effect. Finally, by integrating analytical and experimental results, the influence of soil gas permeability, initial water content, and dry density on vapor migration is investigated. The analysis indicates that higher initial water content and dry density diminish soil gas permeability, thereby restraining vapor migration and alleviating the water accumulation characteristic of Pot Cover effect. The derived analytical framework provides a practical and efficient tool for designing mitigation strategies against Pot Cover effect in cold‐region engineering.