Abstract: This paper presents a case history of a new underground garage deep foundation excavation project near an existing subway in Nanjing. The three-dimensional numerical simulation was used in the modelling, analyzing and predicting the deformation and internal force of the adjacent subway station and its adjacent tunnel structures induced by the entire construction process of the garage deep excavation by using the MIDAS-GTS commercial software. The safety of the existing structures/utilities as well as the structures that are under construction are evaluated based on the analytical results. As a results of the numerical analysis, the design and construction procedures could be adjusted and optimized. The deformation analysis results are also compared with the deformation criteria for the safe operation of the adjacent subway structures. It is concluded that the settlement and the horizontal displacement of stations and other subway elements meet the requirements of subway protection, and the structures are under the safe operation conditions. The tunnel deformation criteria should be based on the requirements of the national standard and Jiangsu provincial standard. The reinforcement depth of the diaphragm wall of the deep excavation needs to penetrate into the medium dense silty sand layer. The MJS construction method is recommended for the joint sealing of the diaphragm wall construction.

Key words: Subway Stations, Shielded Segment, Deep Excavations, Numerical Simulation, Deformation Criteria, Predicted Values