Spatiotemporal evolution characteristics of inundation in multi-level subway stations and inter-station tunnels: A multi-stage quantitative model

• A physical test facility was independently constructed, comprising two multi-level subway station structures connected by inter-station tunnels. • A novel water level chasing effect was discovered in the platforms level of connected station. • An STS model was developed to quantitatively characterize the flooding process and was successfully validated against experimental results. With the accelerating pace of urbanisation, urban flooding disasters are occurring with increasing frequency due to extreme weather events. Subway stations are particularly vulnerable to such flooding, where water ingress can lead to severe casualties and significant property losses. However, the spatiotemporal characteristics of water inundation in multi-level stations and their connecting tunnels remain inadequately understood. In this study, a scaled physical model comprising two multi-level subway stations and two tunnel segments was developed, and similarity ratios for the key parameters relevant to subway flooding experiments were derived. A series of physical experiments were conducted under varying water inflow rates to explore the entire process of station inundation and to analyse the propagation dynamics of floodwater through the stations and tunnels. The inundation process was categorised into three distinct stages: energy release diffusion, stable propagation, and cumulative rise. The multi-stage characteristics of the water level rise process were identified, including a previously unreported water level chasing effect occurring in the platform level of the connected station. A multi-stage quantitative model was developed to characterise the water level rise in multi-level stations and tunnels, and its accuracy was validated through physical experiments. These findings provide valuable references for flood disaster monitoring and early warning systems, personnel evacuation planning, and drainage system design in subway systems.