Temperature Field Law in Cold Region Tunnels and Insulation Effect of Air Curtain

Only laying thermal insulation layer in the tunnel portal section can not completely solve the frost damage problem in cold regions. Therefore, a new air curtain insulation system for cold region tunnels is proposed, a calculation model for temperature field in cold region tunnels subjected to train wind was employed by approaches including superposition principle, separation variable method, and Bessel characteristic function, the distribution law of temperature field in cold region tunnels with different train running speeds and running intervals was studied, the thermal insulation effect of the new air curtain insulation system in cold region tunnels was verified. Only laying thermal insulation layer in the tunnel portal section cannot satisfy the insulation demand for tunnels in cold regions when the ambient temperature is −30 ℃ and the temperature of surrounding rock is 5 ℃, the active thermal insulation measures should be implemented. If the train running speed is more than 200 km/h and the train operation interval is less than 30 min, the whole tunnels need to prevent cold and heat preservation. Finally, it is proved that 50 m air curtain combined with 1050 m insulation layer can meet the thermal insulation requirement of tunnels in cold regions under extreme conditions.