Slurry Trench Stability Control Techniques for North Anchorage Diaphragm Wall Foundation of South Navigation Channel Bridge of Zhangjiagang-Jingjiang-Rugao Changjiang River Bridge
The south navigation channel bridge of Zhangjiagang-Jingjiang-Rugao Changjiang River Bridge is a suspension bridge featuring two suspended spans,where the length of the longer suspended span reaches 2 300 m.The bridge has two towers,and the superstructure consists of steel box girders.Considering the north gravity anchorage is located at the Minzhusha sandbank downstream of the Changjiang River,a composite diaphragm wall foundation is selected to better address the high groundwater level,silty sand and silty clay dominated ground,and the weak bearing capacity and stability of the silty clay layers.The foundation constitutes an exterior and an interior rectangular layers of diaphragm walls,and the gap between the two layers is filled with concrete to create a composite structure to improve the entirety of the foundation and ensure the safe excavation during the construction.The diaphragm walls,on the one hand,serve as a shoring system during the foundation pit excavation and on the other hand,become the permanent load bearing components after the completion of the bridge.To facilitate the construction,the diaphragm wall foundation was divided into 214 trenches,with a maximum depth of 69.5 m,and the trenches were categorized in accordance with their sections,including the I-section,L-section,T-section and crisscross-section trenches.Considering the characteristics of the diaphragm walls as well as the hydrogeological conditions,hydraulic milling machines were deployed for trench formation.Numerical modelling was performed ahead of the construction to determine the key indicators of the slurry trench stability.During the construction,the upper slurry trench was strengthened by triaxial cement-soil mixed piles,and the key indicators of the slurry were controlled in stages,the ground was filled higher and dewatering wells were deployed to control the waterhead between the slurry inside the trench and the subsurface water,The perpendicularity of the completed trenches and the verticality of the concrete-filled steel boxes(reinforcement cages)were controlled,the construction sequences of the trenches were optimized,to reduce the instability risk of the trenches and ensure the construction quality of the diaphragm walls.
suspension bridgeanchoragetemporary-shoring-transformed permanent load bearing structurediaphragmslurry trench stabilityconstruction control
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