Abstract: A new structure of flow guide open tunnel is proposed to minimize the influence of natural meteorological conditions on the frost damage of tunnels in seasonal frozen areas. This structure is designed based on the basic principle of fluid mechanics and the concept of cold/heat accumulation, which is efficient and environmentally friendly. Moreover, the coldproof effect of flow guide open tunnel is validated using ANSYSFluent numerical simulation. The results indicate the following: (1) When the angle between the cold air direction and the tunnel transverse direction ranges from 15° to 75°, the flow guide open tunnel can significantly reduce the velocity of cold flow entering the tunnel. (2) When the angle is less than 45°, the flow guide open tunnel can almost completely isolate the inflow of external cold air. (3) When the angle exceeds 45°, the insulation effect gradually weakens as the angle increases, but it still performs better than traditional tunnels. In the case study, it is found that without the flow guide open tunnel, the length of the tunnel with a temperature below 0 °C is over 1 000 m. However, after implementing the flow guide open tunnel, there is no area in the tunnel with a temperature below 0 °C, indicating a significant coldproof effect.

Key words: seasonal frozen area, tunnel, frost damage, flow guide open tunnel, coldproof effect, fluid mechanics, numerical simulation