Theoretical solution research on air curtain thermal insulation technology at tunnel portal in cold area

In order to ensure that no freezing damage occurs during the service period of the tunnels in the cold areas, the tunnel temperature field model test bench is built according to the similarity principle to study the change rule of the temperature inside the tunnels in the cold season, and a new type of active thermal insulation technology is proposed - air curtain thermal insulation technology at the tunnel portal. Using the principle of superposition of stream function and heat balance, the control equation of air curtain thermal insulation technology is derived, using the principle of superposition and Bessel differential equation to derive the theoretical solution of the radial temperature of the surrounding rock at the tunnel portal section in the cold area under the air curtain action, and finally the feasibility of the insulation technology is verified by taking the Zhengpantai Tunnel as an example. The conclusions of the study show that: the outside ambient temperature and the surrounding rock temperature are the main factors affecting the temperature field of the tunnels in the cold areas; The finite element calculation result shows that the air curtain insulation technology can effectively prevent tunnel freezing damage; there is little difference between the theoretical solution of tunnel radial temperature and the finite element calculation result, and the theoretical solution can provide a theoretical basis for the future practice of the project; the property of the air curtain jet is analyzed, and the air curtain thermal insulation technology can be summarized as heating is primary and air isolation is secondary.