Abstract: The paper focuses on the smoke exhaust efficiency of the vertical shafts in naturally ventilated tunnel fires by using numerical simulation. The impact of the heat release rate (HRR), shaft height, length and width and shaft location on the tunnel ceiling are taken into consideration. The results are compared higher. The smoke exhaust efficiency becomes greater with the increase of the shaft length and width. Besides, it is found that when the shaft is located on the centerline of the tunnel ceiling, more smoke will be exhausted in comparison with that the shaft is located on the tunnel side, and the smoke can be controlled well. Furthermore, the proposed model can predict the smoke exhaust efficiency of the shaft in the naturally ventilated tunnel fires.

Key words: tunnel fire, natural ventilation, vertical shaft, smoke exhaust efficiency