Study on the influence of airflow on the temperature of the surrounding rock in a cold region tunnel and its application to insulation layer design

To show the influence of airflow on the temperature of the surrounding rock in a cold region tunnel, a temperature field model was developed. The model includes temperature control equations of the surrounding rock, air temperature field control equations in the tunnel and wind flow control equations of the turbulence field. On this basis, a numerical analysis method is used to discuss the temperature field change law of the surrounding rock and the thermal insulation measures of the Galongla tunnel in Tibet under the condition of ventilation. The study results show that (1) the air temperature and air speed are two important factors that significantly affect the temperature distribution of the surrounding rock in the tunnel and (2) because of the ventilation effect, the temperature of the surrounding rock falls below 0 °C, and adverse conditions appear at the inlet and outlet sections of the tunnel during the coldest month (January). Further research shows that heat preservation material, such as a phenolic layer with a thickness of 6 cm laid on the secondary lining surface, could effectively protect the Galongla tunnel and rock from freeze and thaw damage if placed for 600 m into the inlet section and 400 m from the outlet section of the Galongla tunnel.