This paper presents the methodology and results of comprehensive three-dimensional finite element analyses which were performed to assess the potential impacts of tunneling under an existing subway tunnels as well as potential impact of tunneling under an existing bridge. The finite element models took into account all relevant components of the construction process including the soil behavior, shield tunneling, pre-cast concrete segmental lining and the tail void grouting. The models also accounted for stage construction and detailed shield-driven tunnel boring machine (TBM) processes including applying balancing face pressure as well as injecting bentonite slurry through the TBM shield. This study has demonstrated that the predicted tunneling-induced impacts on the existing structures can be effectively mitigated by using controlled shield-driven TBM tunneling.
