Monitoring and analysis of the temperature field of a cold-region highway tunnel considering the traffic-induced thermal effect

In this paper, the tunnel temperature (air, structure, and rock) and wall heat flow were monitored in-situ for 63 days in cold and warm terms. The in-situ monitoring results reveal that the trafficinduced thermal effect (TTE) is one of the main factors inducing tunnel temperature variation. The tunnel wall temperature change rate caused by traffic-induced thermal effect is 20.53-43.18% in the cold term. A simplified analytical solution for the tunnel wall temperature is proposed based on Green's function and verified by the monitoring data in this study. The influence coefficients of traffic flow formed by different vehicle types on the tunnel wall temperature in the cold and warm terms are obtained using an optimized machine learning method. The impact ratio is LDV:HDV: HDT = 6:1:1 in the cold (that of LDT is minimal); LDV:HDV:LDT: HDT = 1:8:4:10 in the warm. The assumed tunnel heat absorption ratio (THAR) ranges from 0.19 to 2.05% in the cold term and 0.22 to 0.52% in the warm. The thermal loss degree in tunnel lining is lower than that of ignoring the traffic-induced thermal effect in the cold term. TTE increases THAR by about 1.45% and partly delays the heat dissipation of the tunnel wall. Furthermore, a dynamic network model with vehicles as moving heat sources is established to investigate the thermal effect of different vehicle types. The study results provide reference to new ideas and calculation solutions for designing cold-region highway tunnels and implementing new energy utilization systems.