Simulation of subway flood evacuation based on modified social force model

Abstract

The issue of crowd evacuation during sudden floods in subway stations has gained increasing attention in recent years. However, previous studies have not sufficiently examined the influence of flood flow characteristics, such as location and velocity, on pedestrian evacuation. This gap has limited the effectiveness of current flood evacuation models for subway stations, restricting their utility in formulating robust emergency evacuation strategies. In response, this paper introduces a modified social force model that integrates the combined effects of flood flow depth and velocity at various station locations on pedestrian movement, while also accounting for the role of obstacles during flood evacuation. A case study of an actual subway station under flood conditions demonstrates that flow presence notably reduces evacuation efficiency, with varying effects depending on location. Evacuation efficiency generally declines initially before improving as flood conditions persist, reaching its lowest point at a platform flood velocity of 0.5 m/s and highest at 2 m/s. On staircases and escalators, increased flood flow velocity correlates with reduced evacuation success rate. In terms of emergency response, strategically placing obstacles in flooded areas enhances evacuation efficiency, reducing evacuation time by up to 16.1 % and improving the success rate by as much as 17.8 %. The key contribution of this study is the introduction of a new methodology for flood evacuation research in subway stations, offering a scientific basis for designing effective emergency evacuation plans and safety measures.