Abstract: The distribution characteristics of the temperature fields in extra-long tunnels in cold regions are closely related to natural wind speed. A case study is conducted on a highway tunnel in western Sichuan in a high-altitude area, and on-site investigations, evaluations, and numerical simulations are used to examine the influence of wind flow on the temperature fields of tunnels under construction and penetrated and operating tunnels. The findings are as follows: (1) During tunnel construction, mechanical ventilation significantly impacts the temperature field in the tunnel, increasing the influence of cold air outside the tunnel on the temperature field inside and extending the negative temperature length in the tunnel. (2) Under unidirectional airflow, the temperature field in the operating tunnel is low at the tunnel inlet end and high at the outlet end. The longitudinal temperature field presents asymmetric characteristics. (3) For long operating tunnels in cold regions, the cold wind outside the tunnel does not affect the temperature field in the tunnel when there is no wind or a gentle breeze. (4) When there is alternating airflow at the tunnel entrance, the temperature in the penetrated tunnel is generally low at the entrance and high in the middle area, and the longitudinal temperature field frequently presents a parabolic shape.

Key words: tunnels in cold regions, natural wind, temperature field, unidirectional ventilation, antifreeze design