To systematically investigate the issues of tunnel overheating and excessive humidity, this study integrates theoretical analysis, experimental research, and numerical simulations. It examines the coupled heat and moisture transfer behavior in the surrounding rock of metro tunnels and its impact on the tunnel’s thermal and humid environment. Based on the theory of heat and moisture transport in porous media, a coupled mathematical model is developed using relative humidity and temperature gradients as the driving potentials. Taking into account the climatic zoning of China, Beijing, Shanghai, Guangzhou, and Kunming are selected as representative cities for cold, hot summer/cold winter, hot summer/warm winter, and temperate climate regions, respectively. The interannual variation characteristics of the thermal and humidity conditions inside metro tunnels in these cities are analyzed and compared. The results indicate that across different climatic zones, higher outdoor peak air temperatures lead to higher peak air temperatures inside the tunnels. The thickness of the thermal regulation zone is primarily influenced by the initial rock temperature and the annual average atmospheric temperature. The thickness of the moisture regulation zone is affected by both the annual temperature fluctuation and the annual average relative humidity, increasing with greater annual atmospheric temperature variation.
Ma et al. (Sat,) studied this question.