Subway operations generate substantial heat, and inadequate dissipation can progressively degrade tunnel thermal conditions. The thermal distribution within the surrounding rock is critical for calculating the load on subway environmental control systems. However, the heat transfer patterns in the surrounding rock for intersecting tunnels remain poorly understood. Therefore, this study employs COMSOL software to numerically analyze the impact of intersecting line layouts on the temperature field distribution within the surrounding rock. Results indicate that when tunnels intersect, heat accumulates in the surrounding rock near the intersection. Compared to the single-tunnel structure, intersecting tunnels exhibit higher peak temperature when reaching dynamic thermal equilibrium, and the time required to achieve equilibrium is longer. Reducing the vertical spacing between intersecting tunnels concentrates heat within the intersection zone, leading to elevated temperature in that area. However, when the vertical spacing exceeds 12 m, the numerical value no longer exhibits significant variation with vertical spacing. The intersection angle also influences the temperature distribution characteristic and numerical value. The smaller intersection angle causes heat to concentrate within the crossing zone, leading to an overall increase in surrounding rock temperature within that area. Additionally, the rate of temperature increase in the rock mass at the intersection zone and the magnitude of temperature at dynamic equilibrium are significantly influenced by geographical factors. The lower the ambient temperature in the climate zone where the intersecting subway tunnels are located, the faster the temperature rise rate at the intersection zone. When heat transfer in the rock mass reaches dynamic equilibrium, the temperature difference at the same monitoring point can reach approximately 10°C between severely cold and temperate regions.
Zheng et al. (Thu,) studied this question.