Crowd safety assessment for flood evacuation in subway platform tunnels

Abstract

Flood disasters occur frequently worldwide, causing a large number of casualties and property damage. Urban subway stations are one of the most vulnerable places to flooding. Therefore, to evaluate the flood hazard for passengers in subway stations, an evacuation safety assessment method is proposed in this paper. The flood inundation process is firstly simulated, and the flood depth and flow velocity in subway stations are obtained based on the hydrodynamic model. Secondly, a crowd evacuation model considering the dynamic flood impacts is established, and the simulation results are validated through the qualitative and quantitative methods. Thirdly, the ASET is calculated based on the critical instability status of pedestrians in floods, and the RSET is obtained based on the simulated evacuation time. Finally, the evacuation safety index (ESI), namely the difference between ASET and RSET, is proposed to accurately identify the danger and quantitatively assess the crowd safety at both micro and macro levels in flood scenarios. The results indicate that the staircase areas are more dangerous due to the large water speed, especially under the large inlet flow and evacuee number. Moreover, with the increase of preparation time, the ASET significantly decreases while the RSET increases notably, making it difficult for the crowd to evacuate safely. The study provides useful insights for flood hazard assessment in subway stations, which can help the emergency department to make timely decisions and formulate evacuation plans to ensure the safety of passengers in sudden flood events.