Abstract: In order to study the influence of effects of temperature field distribution in railway tunnels in cold regions on their anti-freeze design, 5 typical tunnels are selected from 3 operating railway projects in high latitude severe cold regions to test and study the temperature field distribution law in tunnels. On this basis, effects of temperature field distribution in tunnels in cold regions are put forward, and the optimization of anti-freeze design of high altitude portals is preliminarily analyzed according to the temperature field distribution law in tunnels. The research results show that: (1) In winter, the temperature field distribution in tunnels in cold regions has obvious chimney effect, shielding effect, scale effect, and cold bridge effect. (2) When railway tunnels are subject to thermal potential difference, static pressure difference between portals, and atmospheric natural wind pressure, the static pressure difference between portals dominates and produces obvious chimney effect. In winter, there is obvious non-uniformity in the longitudinal distribution of air temperature in long railway tunnels in cold regions, resulting in continuous flow of cold air outside tunnel from low altitude portal to high altitude portal, which intensifies the heat exchange between inside and outside tunnel. (3) For tunnels whose alignment intersects the prevailing winter wind direction at a large angle, the ratio of their static pressure difference between portals to thermal potential difference during the winter testing period is half of that of tunnels whose alignment is basically consistent with the prevailing winter wind direction. This indicates that it is beneficial for thermal insulation and anti-freezing of tunnels if their alignment is perpendicular to or intersects the prevailing winter wind direction at a large angle in cold regions. (4) For long "double spur grade" railway tunnels in cold regions, the anti-freeze protection length at the high altitude portal can be shorter than that at the low altitude portal. For long single-slope railway tunnels in cold regions, the anti-freeze protection measures for the high altitude portal can be weaker than those for the low altitude portal.

Key words: railway tunnels in cold regions, temperature field effect, distribution law, engineering countermeasures, dominant factors