Length Design of Mountainous Highway Tunnel Transition Section at Entrance and Exit Based on Temperature Field

To analyze the temperature response of pavement structure inside and outside mountain highway tunnels and determine the reasonable length of transition section, a finite element model of temperature field was established based on the climate and practical engineering in Qinling Mountains. The calculation results of model showed that winter has a more significant effect on the longitudinal distribution of temperature field in each layer of pavement structure than summer. And temperature and temperature gradient have unsteady sections along the longitudinal direction near the tunnel portal. Further, a method for determining the longitudinal transition section of pavement was proposed, and the length of the temperature longitudinal transition section was calculated to be 30 m, and the length of the temperature gradient longitudinal transition section was 60 m.