Optimal design of a ultra-large deep excavation in complicated clay

For the optimization design it is crucial to comprehensively study geotechnical investigation reports, geometric parameters of excavations, protection requirements of surrounding environment budget and time limit for the project. In this case, the composite soil-nailing wall is adopted to stabilize the shallow soil layers so that the floor numbers of bracing system can be reduced to only one considering the hardpan under soft soil. Circular reinforced concrete bracings which can form open construction space and cast-in place piles are used together to constitute the retaining structure system. The deformation and stability of the excavation are analyzed by adopting Tongji Qistar and Plaxis 2D. The monitoring work is carried out during the whole construction process. The rationality and effectiveness of the optimized scheme are tested by the results of the analysis and the monitoring data and can be used for similar projects.