The influence of staircase pattern and flood blocking board setting on pedestrian vulnerability in urban underground staircase floodwaters

To study the hydrodynamic process of surface floodwater intrusion into different types of staircases and pedestrian safety evacuation situations (also known as pedestrian vulnerability), four different types of staircases (L-shaped, U-shaped, double split shaped and double combined shaped), are designed． F, which equals to the square of v multiplied by h (v and h are the floodwater velocity and water depth on the staircase respectively), is used as danger index to measure pedestrian vulnerability characteristics in staircase flooding． It is found that the double split type of staircase has the largest safety area range, followed by U-shaped and L-shaped stairs, and double combined type． Impact of adding a flood blocking board at entrance of staircase on pedestrian vulnerability is discussed． High flood blocking board leads to a large reduced rate in pedestrian vulnerability．These data will be helpful for the design and planning of underground space staircases, for flood control and evacuation in underground spaces．