Abstract: Based on the Middle Bridge Project of Chaoyang Dagou that overcrossing the existing metro tunnel in Changzhou City, this paper presents the influence of installations of closely spaced bridge supporting piles on the existing metro tunnels by the field construction monitoring and three-dimensional finite element simulation results. The results show that the closely spaced pilesinstalled by the low disturbance grouting reinforcement around piles and advance support of the steel casing has no significant impact on the metro tunnel structures. During the entirepile construction process, the deformations of the metro tunnel were within the acceptable controlling range, and the tunnel structure was determined to be safe. The metro tunnel structure is sensitive to the external vibro-impact loadings. When the pile installation method was changed to impact drill bits in adverse geological conditions, the influence of vibration on the deformation of track segments inside the tunnel should be carefully considered. The entire process of the pile foundation construction and post-construction service loadingare simulated by the finite element software, and the deformations from the analytical results and field monitoring data are compared. After the external bridge structure loadsare applied, the tunnel mightresult in deformations, therefore, it is necessary to emphasis the post-pile installation monitoring to ensure the safety of the metro tunnel structure.

Key words: Pile Foundations, Metro Tunnel, Construction Monitoring, Numerical Simulation, Deformation