| In recent years,China’s urbanization process has been accelerating.With the frequent occurrence of heavy rains,urban floods caused by extreme rainfall frequently invade underground space,causing great losses to people’s production and life.Therefore,the rapid and accurate assessment of the risk of urban underground space and the setting of corresponding flood control devices are effective ways to reduce the impact of urban flooding on underground space.However,at present,the relevant evaluation models generally have the disadvantages of complex analysis methods,low efficiency and insufficient timeliness.Therefore,it is very meaningful to propose a risk assessment model that is easy to apply in practical engineering.On the basis of assuming that each catchment basin is independent of each other and ignoring the drainage capacity of underground drainage facilities,the easy accumulation of water is generalized into an inverted quadrangular pyramid,thus simplifying the risk assessment model of the underground space,and accumulating water in the city.The complex simulation process becomes more operative and achieves the purpose of effectively assessing the risk of exposure to underground space.A subway station in Xi’an was selected as a case to verify the reliability of the simplified model by comparing the calculation results of the SWMM model and the simplified model.At the same time,two new types of underground space flood control devices were developed,and their structural features and working methods were explained.The main research contents and conclusions are as follows:Firstly,based on the SWMM model,the mathematical principles and modeling process of each module are introduced.When the SWMM model is used to evaluate the risk of underground space exposure,the modeling process is complex and the workload is large,which indicates that it is necessary to construct a simplified risk assessment model for underground space.Secondly,three common urban topography are summarized by investigating the topographical features of a large number of underground spaces.The method of dividing the various types of topographic catchment basins is proposed.Based on the inverted quadrangular pyramids,a simplified model for the risk assessment of underground space is constructed.The calculation method of the water depth is proposed by using the calculation method similar to the reservoir capacity and water depth.In order to reduce the influence of the model hypothesis on the calculation results,and considering the safety,the height of the underground space is recommended,that is,the safety height is increased by 0.15 m based on the depth of the accumulated water.Thirdly,taking a subway station in Xi’an as an example,the measured rainfall and design rainstorm were selected to simulate the SWMM model and the simplified model,and the reliability of the simplified model was verified by the SWMM model.When the design stormwater data and the measured rainfall data with a return period of 50 a are input in the SWMM model,the percentage error between the simulation result and the actual water accumulation depth is 5.20%,which indicates that the SWMM model of the study area established in this paper can accurately simulate the water accumulation and provide a reliable basis for verifying the simplified model.After inputting the measured rainfall in the simplified model,the percentage error between the proposed proposed fortification height and the actual accumulated water depth is 4.00%,indicating that the simplified model can accurately assess the risk of exposure to the underground space.At the same time,the percentage error of the simplified model and SWMM model under different return periods is less than 15%,which indicates that the simplified model can replace the SWMM model,thus improving the efficiency of the risk assessment of the underground space.Fourthly,it is difficult to realize the flood prevention of large space in the prior art,and there are problems affecting the overall aesthetics of the building and the timeliness of flood control.Two new types of flood control devices have been developed to further reduce the risk of water in the city bringing underground space. |
