| Due to the influence of climate change and extreme weather patterns,urban subway systems in several nations have been frequently affected by flood disasters in recent years.The safety of people and property is severely impacted once a flood invades a subway station.It is essential to carry out flood control and disaster reduction of subway stations during flood invasion to enhance the capacity to prevent flooding and other disasters while also protecting the safety of people and property inside the station.This study is based on the Realizable k-εturbulence model and VOF model,which were utilized to conduct out numerical simulation of water flow at subway stations during a flood invasion.Taking Shakou Road Station of Zhengzhou Metro Line 5 as an example,the process of station flood invasion against the backdrop of an extremely heavy rainstorm was studied,the invasion mechanism and law of subway station flood were analyzed,and flood prevention and evacuation strategies for urban subway stations were proposed.The following are the particular research contents:(1)The relationship between the static water depth at the entrance and the flow rate for a single width was fitted based on the water depth flow relationship at the entrance of the staircase.A numerical model of the staircase flow field was established based on the Realizable k-ε turbulence model and the Volume of Fluid(VOF)method.The model was validated by current research on staircase flow test results,and it was shown that the coupled Realizable k-ε turbulence model and VOF method can accurately simulate the flow process.Taking the entrance staircase of Shakou Road subway station as an example,the time and process of water flow on pedestrian stairs and escalators were simulated.The effects of the intermediate rest platform,staircase slope,and entrance water depth on the water flow characteristics on the stairs were analyzed.The escape control index F,represented by water flow speed and depth,was used to evaluate the evacuation risk of personnel on the stairs.(2)The Realizable k-ε turbulence model and VOF method were used to construct a numerical model of the subway station water intrusion process based on the theory of air-water two-phase flow.Taking the Shakou Road subway station as an example,a numerical simulation of the water flow process of the subway station under flood intrusion was carried out.The impacts of closing and opening tunnel flood gates,varied numbers of inlet water input,and different inlet water flow depths on the flood intrusion process were investigated.The water level variations and flow patterns in the station hall,platform,stairs,and tunnels were obtained by a real-time simulation of the inundation process of subway stations from flood invasion to basic stability.(3)The water flow characteristics and patterns inside subway stations were analyzed using numerical simulation results of water flow in subway stations,and the efficiency of flood control measures in the flood invasion process was evaluated.The flood protection measures of subway stations are deeply studied,and some additional measures are proposed to supplement the existing flood control measures.The safe evacuation time of underground space with flood control measures was calculated based on the critical water depth for safe evacuation of underground space and the theory of safe evacuation,taking into account the relationship between the rate of increase in water flow depth and flow rate above ground and underground,as well as the impact of flood control measures. |
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