Abstract: The transverse settlement induced by the construction of a parallel shield tunnel alongside the building has raised considerable attention, whereas few studies focus on the longitudinal settlement. Therefore, the spatial deformation of ground developed from this tunneling form is investigated. In this study, some field measurements from the shield tunnel section of Tianjin Metro Line 6 parallel to four similar masonry buildings in vicinity are analyzed first, and the deformation pattern is established. Then, a hardening soil model calibrated against field measurement, considering small strain stiffness, is implemented in a three-dimension finite element simulation to evaluate the longitudinal deflection of the buildings, the ground deformation, and the soil stress distribution. Additionally, the effect of building aspect ratio is discussed. The simulation results show that tunneling-induced sagging deformation develops along the longitudinal direction of the building, and the settlement at the middle of a longitudinal wall is twice of that at the corners. Therefore, the study of tunneling parallel to buildings cannot be simplified to a plane strain problem. The building construction and tunneling activity result in the soil above the tunnel crown experiencing a complicated stress history, which can be divided into six stages. In longitudinal direction, compared with the part below the building foundation corners, the soil in the middle initially behaves larger compressive deformation due to building construction, followed by greater unloading deformation caused by tunnel excavation. In addition, the longitudinal sagging is significantly reduced for the buildings with aspect ratio less than 2.

Key words: shield tunneling, parallel tunneling, building settlement, finite element method (FEM), HS-Small model