Analysis of the Influence of Pile Underpinning of the Pile Group Under the Viaduct of the Overlapping Shield Tunnel on the Surrounding Environment.

The purpose of this paper is to propose and verify pile foundation underpinning technology for overlapping shield tunnels crossing pile groups and to predict and analyze the impact of overlapping tunnel excavation on the surrounding environment. Based on the pile foundation underpinning project of the Harbin Metro overlapping tunnel crossing the viaduct, a three-dimensional numerical model is first established to simulate the pile foundation underpinning process. Then, the rationality of the model is verified by comparing field monitoring data with numerical calculation data. The influence of the overlapping tunnel crossing the underpinning area is predicted and analyzed, and the mutual influence trend between the overlapping tunnels and the tunnel and underpinning area is explored. The results show that the trend of the settlement monitoring data of the cap and pier are consistent with that of the simulation results. Considering mutual coordination of the bridge structure, the rationality of the model is verified. In the underpinning process, the settlement of the underpinning pile is mainly caused by underpinning. The D52' pier and underpinning cap exhibit large settlement, but they still meet the safety requirements. During overlapping tunnel excavation, the vault settlement and segment bending moment in the underpinning area can be effectively controlled, while the surrounding environmental displacement also meets the requirements. Therefore, the pile foundation underpinning technology proposed in this study can be adopted to effectively solve the problem of overlapping tunnels crossing viaduct foundations, protect bridge structures and the surrounding environment, and provide a reference for similar projects. [ABSTRACT FROM AUTHOR]