A new sustainable energy based freeze proof method for drainage system in cold-region tunnels: A case study of Tianshan Shengli Tunnel

In order to solve frost damage problems in cold-region tunnels, a new sustainable energy based freeze proof method for tunnel drainage system is proposed. The method is applied to Tianshan Shengli Tunnel, China as a case study to show the concept and details of tunnel drainage system ground heat exchangers (GHEs) including calculation of active heating length and maximum heating load, design of heat extraction in cross tunnel, the segmented design method. Long-term performance of tunnel drainage system GHEs is also fully discussed. Multi-field simulations are performed to achieve corresponding thermal responses of the tunnel drainage system GHEs. Results show that anti-freezing measures provide an initial heating length 900 m of the drainage system at the entrance of Tianshan Shengli Tunnel during full life cycle. When the tunnel drainage system GHEs are employed, the heating length can be reduced to 600 m. Maximum total heating load of the tunnel drainage system in heating period is 84.40 kW. The calculation method of segmented heating load is suggested for precise prevention and control of frost damage in cold-region tunnels, owing to varying tunnel air temperature with the distance from the tunnel entrance. The use of boiler heating in winter will enhance the compensation between operation and recovery period and provides good long-term performance. This study provides a potential reference for antifreeze design of cold-region tunnels utilizing geothermal energy.