Abstract: The impact of fire-shaft distance on the smoke flow properties and smoke exhaust efficiency in naturally ventilated tunnel fires was studied by numerical simulations. The fire–shaft distance and the cross-section of the shaft are taken into consideration. The numerical simulation results indicate that with the increase of the fire-shaft distances, the mass flow rates of the incoming smoke before the shaft increase, however the smoke exhaust efficiency and air entrainment of the shaft decrease. Besides, when a small fire-shaft distance is employed, more heat can be exhausted and lower temperatures downstream the shaft can be generated, and the smoke can be controlled within a small range. Moreover, as the shaft cross-section increases, the smoke exhaust efficiency of the shaft becomes great and more smoke can be exhausted under a wider shaft. From the resulted obtained in this work, when a large interval of adjacent shafts is set, it is suggested that a large shaft cross-section and a large shaft height be used.

Key words: natural ventilation, tunnel fire, fire-shaft distance, smoke flow, smoke exhaust efficiency