3D FE coupled simulation of TBM tunnelling and station excavation

Growing demand for mobility in major cities around the world has led to the expansion of existing underground transport networks, with the aim of alleviating congestion and promoting sustainable growth. This usually involves deep excavation and tunnelling in densely populated areas, often in close proximity to existing buildings and infrastructure. Limiting ground movement is therefore a key design priority. Further complications arise when considering the interaction between tunnelling and station excavation. This problem is usually simplified using a decoupled approach, whereby tunnel and station excavations are simulated separately to limit computational effort. The computed displacement fields are then superimposed. Conversely, coupled 3D tunnel-station numerical models can accurately reproduce the effects of the two interacting excavations, albeit at a much higher computational cost. This paper discusses aspects of the interaction between mechanised tunnelling and station excavation. The study focuses on Piazza Venezia station on Line C of the Rome Underground. A 3D finite element (FE) model has been developed to simulate the tunnelling sequences, the station excavation, and the interaction with the surrounding historic buildings. The analysis results suggest that, in the case of a very stiff excavation box, the station's stiff headwall induces a shielding effect on the propagation of tunnel-induced displacements.