Study on smoke propagation in tunnel construction of a hydropower station: A full-scale fire experiment

In this study, full-scale fire experiments were conducted in a hydropower station to investigate smoke propagation during tunnel construction. The flame height, smoke temperature and stratification, smoke descent and spread velocity were analyzed via measurements and on-site observations. The initial combustion stage was largely affected by ignition source during tunnel construction for diesel pool fire, and the average flame height in the fully developed stage could reach 1.4–2.1 m in experimental fire scenarios. The gradient of the smoke temperature evolution near the fire was the opposite for the upstream and downstream regions. The longitudinal temperature distribution was concentrated in a small range at the heights of the smoke layer, and gradually decreased by air entrainment as the height decreased, while further increasing in the lower half of the tunnel height in the near-fire region under heat radiation from the fire source. Moreover, distinct and stable smoke stratification formed during the fully developed combustion stage, and the smoke layer interface was at approximately half the tunnel height. Smoke descent was aggravated in the decay stage of combustion, and the fire risk remained high after the fully developed period. The smoke front spread velocity was empirically determined for the full-scale tunnel fire scenarios. Conclusions from full-scale experiments can support smoke control design and on-site fire emergency response plans for hydropower stations.