Abstract: A novel three-dimensional printed refined scale model for tunnels in cold regions is developed using a model test method to explore the freezing response patterns of railway tunnel drainage systems in such regions and clarify key points regarding the cold and frost resistances of such tunnels. This model provides a complete and transparent drainage structure, enabling a visual representation of the freezing process in tunnel drainage systems in cold regions. Based on this model, a series of freezing response tests is conducted for drainage systems under various temperature conditions. The following results are drawn from this study. (1) The temperature field varies considerably above the tunnel arch foot, with the maximum variation being observed at the widest span of tunnel. By contrast, the temperature field below the tunnel arch foot shows small variation, highlighting the important role of the deep-buried central ditch. (2) Under all temperature conditions, the freezing of the tunnel drainage system begins at the side ditch, followed by the circumferential blind pipe. The transverse guide pipe and central ditch do not freeze during tests. Furthermore, the connection between the side ditch and circumferential blind pipe is identified as a critical weak point for frost resistance; hence, insulation measures for this area should be strengthened.

Key words: railway tunnels in cold regions, three-dimensional printing, scale model, model test, drainage system, freezing pattern