Abstract: The influence of tunnel curvature on the design of the insulation layer and the longitudinal temperature field of the Jinjiazhuang tunnel of the YanqingChongli expressway in Hebei, China is discussed using theoretical derivation and computational fluid dynamics simulation methods; moreover, calculation methods for the laying length of the insulation layer under different tunnel curvatures are proposed. The research results show the following. (1) The curvature of the tunnel causes an asymmetric flow of air in the tunnel, which further causes an asymmetric convection heat transfer on the left and righthand sides of the tunnel, and an asymmetric temperature distribution. The greater the curvature, the more serious the asymmetry. (2) The air velocity difference in the boundary layer inside and outside the tunnel increases with increasing curvature, and the offset effect caused by centrifugal force appears 150 m away from the tunnel entrance and quickly stabilizes. (3) The temperature asymmetry in the tunnel caused by the curvature is considered in the proposed formula for calculating the length of the insulation layer, and the formula can be used to calculate the laying length of the insulation layer of the tunnel with various curvatures.

Key words: curved tunnel, tunnel in cold area, laying length of insulation layer, computational fluid dynamics simulation, theoretical derivation