Near-sea Area(Xiamen)Subway Underground Station Side Wall Cracks And Leakage Prevention

As an island city,Xiamen has a high groundwater level and complex rock structure.Its subway tunnels and underground subway stations are facing many challenges.The cracks and leakage of the outer walls of subway stations are one of the most difficult problems.Based on the actual construction practice of the underground subway stations in Xiamen,this paper summarizes the experience and lessons,which will provide the reference for the similar projects in the future.This paper investigates and studies the cracks and leakage of the outer wall of the subway station in Xiamen at present.It analyzed and summarized the main causes of cracks and leakage of the outer wall of underground railway from two stages of survey design and construction organization.Among them,the cause of cracks and leakage of the external walls in the stage of exploration and design are the incomplete geological exploration,design defects of overlapping walls,the nature of concrete itself and the absence of cracks in super-long structures.In the aspect of construction,the influence of gravity center and internal force system,inadequate treatment of construction joints,sudden change of bracing stress,improper construction operation,structural creep and poor waterproof measures are the main factors.According to the construction practice case of Houcun Station in Xiamen,the following preventive measures are summarized as follow:First,the precise site selection,detailed geological prospecting,reasonable enclosure measures and advanced concrete mix design are the preventive measures in the exploration stage.Second,in the construction stage,the prevention measures take full account of the deviation of the center of gravity of the structure,and then,the components of each trough section are arranged according to the working procedure including temperature measurement and maintenance after concrete pouring,scientific control of reinforcing steel bar,formwork support,concrete pouring vibration,demolition maintenance and waterproof layer construction,and advanced construction management such as monitoring&early warning and first piece acceptance system,etc.In this project,three new technological measures of pre-embedded cooling pipe,structural buffer layer and non-destructive induction joint have been innovatively adopted.Meanwhile,it carries out the physical experiments to verify.Based on the corresponding experimental monitoring data and the practical experience of the project,the research team adopted the optimization of construction scheme and construction management measures,including the control of raw material and mix proportion,the processing and installation of the steel bar,the control of formwork and support process,the control of concrete pouring and vibration process,the control of concrete demolition,the control of concrete maintenance and so on.Meanwhile,it implements the first piece acceptance system.The final acceptance record shows that the crack and leakage control of Houcun Station has achieved remarkable results.