Abstract: Based on the theory of “three regions”， a combined differential equation is established to solve the problems of hydro-thermal coupling in cold regions considering water transfer and water ice phase transition. The numerical simulation of temperature field coupled with water field was carried out by COMSOL multi-physics software， and the numerical simulation results were compared with the results of soil column freezing experiment to verify the effectiveness of the hydrothermal coupled numerical simulation model. By considering the theory of frost heave， the stress field governing equation of the tunnel in the cold regions is deduced， and the thermo-hydro-mechanical coupled model of the tunnel in the cold regions is established by using the relationship between pore ice and frost heave rate. Finally， the temperature field， humidity field and stress field were simulated by taking the Musui tunnel between Mudanjiang and Suifenhe as a case study. The results show that the change in external temperature has a great impact on the tunnel after excavation. The thickness of the freezing ring of the tunnel hole gradually increased with time and reached a maximum depth of about 2meters in January.

Key words: cold region tunnel, hydro-thermal coupling, thermo-hydro-mechanical coupling, frost heave, COMSOL