Research On Key Technologies Of Waterproof Design For Ultra-deep Metro Station

With the rapid development of social economy and the continuous improvement of urbanization level in China,the contradiction between urban development and shortage of various resources has become increasingly prominent,and the development and utilization of urban underground space has become more and more in-depth,which has also made the urban rail transit develop historically.As the backbone of China's urban rail transit system,Metro is a powerful tool to improve urban traffic.Among them,the subway station is the place where passengers take,land,transfer and wait for the train,and it is the most important link in the planning of the subway system.However,most of the subway stations are built underground,especially in water-rich and weak strata such as Shanghai.Most of the newly built subway lines intersect with the existing ones and are forced to continue to bury deep,forming a large number of ultra-deep subway station structures,whose structures have been affected by various complex factors for a long time.In the construction and operation of ultra-deep Metro station,once leakage occurs,it will seriously threaten the operation and structural safety of the metro.Therefore,effective waterproofing technology is particularly critical.With the large-scale development and construction of metro,the scale and depth of metro stations are increasing.The unreasonable setting of induced joints is easier to increase the number of structural cracks in the stations,but it will bring more and more seepage problems which are difficult to eradicate.Therefore,in order to solve the leakage problem of metro station and improve the waterproofing efficiency of ultra-deep Metro station,it is necessary to make a thorough and systematic study on the setting mode of induced joints in the key technology of waterproofing design of ultra-deep Metro station.Based on the background of the construction of Lujiazui Ultra-Deep Metro Station and Huangpi South Road Ultra-Deep Metro Station on Line 14 of Shanghai Rail Transit,a three-dimensional numerical calculation model of Lujiazui Station is established by using finite element analysis software,and the setting mode of induced joints is studied by crack propagation behavior.On this basis,the layout of induced joints in subway station structure is carried out,and the rationality of the arrangement scheme of induced joints is verified by comparing with the model without induced joints,and the spacing of induced joints is optimized by parametric analysis.In addition,some suggestions for the layout of the induced joints of the station structures with uneven stiffness distribution are provided by combining calculation and analysis.The temperature field and stress field of composite wall of concrete structure of Huangpi South Road ultra-deep metro station are simulated by finite element analysis software.The effectiveness of induced cracks applied in concrete structure in specified section is verified by using elastic-plastic damage constitutive model of concrete.By setting different spacing of induced cracks,a comparative analysis is made on how to reasonably set spacing of induced cracks.At last,according to the waterproofing design of induced joints,combined with the actual project,the comparative use effect is analyzed.The results show that setting induced joints can reduce the temperature stress in the area without induced joints,increase the temperature stress in the adjacent section of induced joints,guide cracks to occur in the designated section,and effectively prevent the disordered cracks in concrete structures;when arranging induced joints in ultra-deep Metro stations,they should be evenly arranged along the long axis of Metro stations;it is suggested that the spacing of induced joints should be 25m~30m,and the section should be weakened.The maximum crack propagation depth is 0.4m.In addition,for irregular and ultra-deep Metro stations,two unequal spacing induced joints can be set up at the junction of sudden stiffness change.For special structural stations with sudden stiffness change,induced joints need to be set not only at the junction of sudden stiffness change,but also in each independent section to reduce it.There are few cracks and damages in the main structure.The research in this paper can provide reference for the design of induced joints and waterproof engineering application of ultra-deep Metro station.