Field measurement and analysis of subway tunnel thermal environment in severe cold region

Recently, subways in China's severe cold regions have developed rapidly. Harbin, a typical city in a severe cold region, can reach the lowest outdoor temperature of −37.7 °C in winter, making the thermal environment of the underground tunnels a huge challenge. Due to the complexity of the subway environment, there are few long-term field measurements, and the research on entrance and exit lines is often neglected. In this study, the thermal environment of Harbin Metro Line 1/3 and the entrance and exit lines was measured and studied, the heat production of train operation and annual heat storage heat was calculated. The results show that climatic conditions, burial depth, operating phase of the tunnel, passenger flow, and driving interval have an impact on the thermal environment of the tunnel. The daily average temperature difference between the two ends of the entrance and exit lines reached a maximum of 27.4 °C in winter. The average air temperature of Line 1 in summer, transition season and winter were 4.0 °C, 1.0 °C and 2.5 °C higher than that of Line 3, and the heat generated per hour was 201 MJ–242 MJ higher than Line 3. Furthermore, the heat storage capacity of tunnels in severe cold region was significantly higher than that in hot summer and warm winter region, the maximum difference was 823 GJ. The monitoring data are useful for both analytical and numerical studies and this study provide a valuable reference for the construction and operation of subways in severe cold regions.