The criterion of ice lens initiation is a critical mechanical property that is essential for investigating the interactions between water and heat transport mechanisms in frost heave studies. Owing to the complexity of the ice lens initiation phenomenon, the criterion of ice lens initiation varies depending on different theoretical models, which makes uniform evaluation difficult. To investigate the intricate physical mechanism of the ice formation criterion, a unified theoretical model is proposed to simulate the ice formation process of four commonly used criteria (the neutral stress criterion, unfrozen water film criterion, pore ice pressure criterion and empirical water content criterion). The physical mechanisms of the different assessments are investigated by studying the frost heave, ice lens distribution and frost heave rate for four different soil properties. The results indicate that the neutral stress criterion is more accurate and stable for ice formation than the current wellestablished criterion for ice lens initiation. Furthermore, the study reveals significant similarities between the pore ice pressure and the unfrozen water film. The empirical water content is prone to significant errors because of the absence of a reliable physical basis.
