Structural Responses of Existing Metro Stations to Adjacent Deep Excavations in Suzhou, China

Abstract

Situations in which deep excavations are made adjacent to metro stations in service are common in the development of underground space. However, the structural responses of existing metro stations to adjacent deep excavations and their safety criteria are still not fully understood. Through a series of numerical parametric studies and comparisons with case histories reported in the literature, this paper examines both the structural forces and differential displacements of existing metro stations induced by adjacent excavations. To consider the effect of stress history, the hardening soil small-strain model (HSS) was employed, and the building process of existing metro stations was included in the numerical simulations. The effects of key factors, e.g., the distance between existing metro stations and new excavations and the depth of new excavations, governing the responses of existing metro stations to adjacent excavations are investigated and quantified. In addition, the barrier effects of existing metro stations on the deformations of adjacent excavations are also investigated. On the basis of the numerical analysis results, some major findings were obtained: (1) excavation depth, He, and distance from the existing metro station, D, were the key factors affecting the structural responses of an existing metro station to the adjacent excavation; (2) the rotation and shear effects of an existing metro station induced by the adjacent excavation varied with D/He and could be reversed in direction; (3) the bending moments in critical sections changed with D/He and the additional bending moments in the sections had a linear relationship with the rigid column rotations; and (4) because of the barrier effect of the metro station, both lateral wall deflections and ground surface settlements induced by the adjacent excavation on the side of the metro station were smaller than those without a metro station nearby. The findings yielded from this study should provide practically useful references for engineers to assess the structural performance and rail safety of existing metro stations affected by adjacent excavations so that appropriate countermeasures can be adopted.