Flood Control and Drainage Design Standards for Sunken Metro Vehicle Base

［Objective］ As a special form of space utilization for vehicle base, sunken metro vehicle base faces greater risk in flood control and drainage. However, currently there are no available specifications and standards in this regard in China. Therefore, it is necessary to conduct in-depth research on the flood control and drainage design capacity of sunken vehicle base, clarify the relevant content in specification and standards to provide design reference for such projects. ［Method］ Relying on the Qianyin Parking Lot project of Ningbo Metro Line 5, the design requirements in existing specifications and standards for flood control and drainage are analyzed, as well as the flood prevention and control scheme of the sunken vehicle base. The flood control and drainage design schemes for different areas in sunken foundation pit are compared and analyzed according to 50-year and 100-year rainstorm return periods. ［Result & Conclusion］ The sunken vehicle base should adopt ′reliable measures for waterlogging prevention and drainage′ to meet the basic requirements in this regard. In terms of flood control, the flood wall top elevation of sunken vehicle base and the pavement elevation at entry/exit should be higher than the 100-year flood level plus the safety height, and the height difference between the flood wall and the surrounding ground should be higher than the plot waterlogged level under 100-year rainstorm return period condition. In terms of drainage, the principle of ′high water and high drainage′ should be adopted for the drainage of the cover roof area over sunken foundation pit. The roof drainage capacity should be designed according to 100-year rainstorm return period, and the water should be directly discharged out of the foundation pit through gravity flow. The open area in the pit adopts pumping and drainage method, and the total drainage capacity of the rainwater pump station is designed according to 100-year rainstorm return period.