Freeze depth predicting of permafrost subgrade based on moisture and thermal coupling model

Water and heat conditions and the interactions between them are the key factors in highway freeze damage. A 2-D moisturethermal coupling model has been developed to analyze the temperature profile of the permafrost subgrade and to more thoroughly understand the moisture and thermal transport in subgrade soil. The model accounts for the effects of heat generation, internal conduction and convection, and moisture transport to accurately predict the freeze depth of the subgrade. This model formulates the control equation of the temperature field, the moisture field and their coupling. A commercially available finite element package (ANSYS) is used to solve the simulation. The numerical calculations are compared with in-situ test results on the Qinghai-Tibet Highway and appear to be in strong agreement. The accuracy and precision of the coupling model are superior to the traditional single-field model, which indicates the model's suitability for predicting the freeze depth of the permafrost subgrade. This model can aid in prevention of highway damage by predicting periods of subgrade thaw and elevated water content such that traffic restrictions can be effectively implemented.