A simulation study on risks of pedestrian evacuation from flooded staircases of different slopes in the underground space

To quantitatively assess the risks of pedestrian evacuation through staircases with different slopes when a flood intrudes into the underground space, a numerical model was designed to simulate flood flow patterns on staircase and escalator under different slope conditions (26.6°, 28.2°, 29.1°, 30°, and 35°). A safety index (F (v2, y)) was employed to assess the risks of pedestrian evacuation through the staircase under different slopes. When the water depth at the staircase entrance (under slopes ranging from 26.6° to 28.2°) was 0.3 m and the unit width discharge was 0.28 m2/s, pedestrians safely evacuated the underground space. However, when the staircase slope was beyond 28.2°, the safety index value was higher than the critical value and the flood caused serious threats to them. Therefore, it is suggested that when the underground space becomes flooded, pedestrians should avoid steep slopes and choose a gentle staircase as a safer escape route. The obtained results provide a theoretical guideline for pedestrian evacuation from a flooded staircase.