Abstract: Investigation shows that highway tunnels in cold regions have severe freezing-induced damages,  which affect the safety of the tunnel structure and the tunnel operation seriously. In this study, the freezing-induced damages of tunnels in cold regions, as well as the causes for the damages, are discussed, the concept and approach for the anti-freezing design of the tunnels are summarized, and the calculation methods for the anti-freezing fortification length, the calculation methods for the frost heaving forces, and the status and effect of the application of the anti-freezing measures for tunnels in cold regions are analyzed. Conclusions drawn are as follows: (1) The design concept that "freezing prevention shall be taken as the main measure, frost heaving force resistance shall be taken as the supplementary measure, and the freezing prevention measures and the frost heaving force resistance measures shall be coordinated" shall be adopted for the anti-freezing of tunnels in cold regions. (2) For highway tunnels in cold regions where the groundwater is developed, graded anti-freezing should be designed according to the average temperature in the coldest month. (3) The anti-freezing fortification length determined by the empirical analysis method has certain feasibility, however, it shall be further modified according to the temperature data measured in the field. (4) The calculation model for the frost heaving force on the tunnels in the cold regions has shortcomings in practical engineering applications, while the calculation method considering the non-uniform frost heaving of the freezing circle of the surrounding rock is relatively consistent with the engineering practice. (5) The anti-freezing design of tunnels in cold regions shall focus on the proper handling of the temperature and the groundwater, i.e., the measures for temperature keeping/increasing and the measures for the anti-freezing of the drainage system. Furthermore, the limitations of the temperature keeping/increasing measures and the directions of further researches thereof are pointed out, and the principles for the arrangement of the anti-freezing measures for drainage systems of tunnels under different fortification grades are put forward. Additionally, the key points of the development trends of the anti-freezing technologies for tunnels in cold regions, such as the distribution pattern of the temperature field under intricate factors, the mechanism of the freezing-induced damages, the thermal-insulation materials, and the new thermal-insulation measures, are proposed to solve the problem of the freezing-induced damages of tunnels in cold regions.

Key words: tunnel in cold region; highway tunnel, anti-freezing design, frost heaving force, anti-freezing measure