Analysis of the Influence Mechanism of Thermal Environment in Subway Tunnels postprint

Abstract: To investigate the influencing factors of the thermal environment in subway tunnels, a field measurement campaign was conducted on Changsha Metro Line 2. The results demonstrate that the tunnel thermal environment is primarily governed by train operation frequency and heat generation, while exhibiting weak correlation with outdoor air temperature. During train operations, increased running frequency enhances heat transfer from the tunnel to surrounding rock. When trains pass through, the heat flux consistently directs from tunnel to surrounding rock. However, distinct patterns emerge during non-operational periods: in heating seasons, dominant heat transfer reverses from surrounding rock to tunnel interior, whereas transitional and cooling seasons maintain tunnel-to-rock heat dissipation. Notably, the thermal environment stabilizes significantly during train service suspensions.