The top centralized smoke exhaust mode is commonly used in extra-long or super-long shield tunnels. To reveal the smoke stratification height and range in the centralized smoke exhaust mode at the top of the tunnel fire, it was found through the field hot smoke test of the full-scale tunnel that the smoke could be divided into stable layers and controlled within a certain range in the centralized mode. The smoke stratification height and range under different heat release rates, different exhaust volumes, and different numbers and spacings of exhaust valves were investigated from numerical simulations. The main research conclusions are as follows: 1) for heat release rates ranging from 5 MW to 50 MW, the smoke exhaust system effectively controlled the smoke stratification range within a certain distance under different heat release rate conditions. As the heat release rate increases, the extent of smoke stratification increases. Within the opening range of the exhaust valve, the heat release rate increases, and there was a certain gap in the smoke stratification height. Outside the opening range of the exhaust valve, the greater the heat release rate, the lower the smoke stratification height. 2) When the heat release rate was set at 50 MW and the smoke exhaust rate ranged from 120 m3/s to 260 m3/sunder different smoke exhaust rate conditions, the smoke stratification height barely changes within the opening range of the exhaust valve; in contrast, the smoke stratification height changes greatly outside the opening range, and the smoke stratification range becomes smaller as the smoke exhaust volume increases, thus effectively controlling the smoke distribution area. Therefore, it was suggested that the smoke emission could be increased within the allowable range during engineering design and operation. 3) With exhaust valve distances ranging from 40 m to 140 m and the number of exhaust valves varying from 4 to 8, the distance between the exhaust valves and the number of exhaust valves increase, leading to decreasing smoke stratification height. The smoke stratification range increases, and the number of exhaust valves had a greater impact on the smoke stratification height and range. © 2023, Central South University Press. All rights reserved.
