Abstract: To reveal the temporal and spatial distribution laws of temperature in cold region tunnels, based on the Jinjiazhuang extralong spiral tunnel, the field monitoring method is employed to investigate the variation laws of temperature of the spiral tunnel in cold regions. Furthermore, a threedimensional model is established using numerical simulation to investigate the influence of inlet wind speed and temperature on the temperature field, and the formula of the insulation layer laying length is obtained by fitting the simulation results. The research results reveal the following: (1) The annual average temperature of air at the inlet and outlet of the Jinjiazhuang spiral tunnel increases as the depth into the tunnel increases. However, the annual temperature amplitude decreases gradually, and the annual temperature amplitude at the inlet of the tunnel varies more than that at the outlet. (2) After tunnel penetration, the annual average temperature and temperature amplitude of the same monitoring section decreases and increases, respectively, under the joint action of the relative low temperature outside the tunnel on both sides. (3) The temperature field distribution laws of the tunnel in the straight section are the same as that of the straight tunnel under the same conditions, and the temperature curves of the inner and outer diameters bifurcate from the curved section, i.e., the temperature of the outer diameter side is higher than that of the straight tunnel, while the temperature of the inner diameter side is reversed. (4) The larger the inlet wind speed and lower the inlet wind temperature, more unfavorable the tunnel temperature field. According to the fitting formula, the length of the insulation layer at the inlet of the Jinjiazhuang extralong spiral tunnel should be at least 1 239 m.

Key words: spiral tunnel, cold region tunnel, temperature field; field measurement, insulation layer