Behavior of an Excavation Adjacent to a Historical Building and Metro Tunnels in Shanghai Soft Clays

In this paper, a case history of a deep excavation in Shanghai, which was adjacent to a historical building founded on 27 m long wooden piles and operating Metro tunnels, is presented. The effects of the excavation on the nearby pile foundation and the existing tunnels are investigated using two-dimensional finite element modeling. The predicted maximum horizontal and vertical displacements of the wooden piles are 15.8 mm and 7.6 mm, respectively. The horizontal and vertical movements of the utility tunnel and Metro tunnel are all less than 10 mm, which satisfies the current design criteria for controlling the deformation of the Metro tunnels in Shanghai. The results indicate that the design and construction measures of this excavation can effectively limit the deformation of the soils and therefore the impact of the excavation on the adjacent piles and the tunnels can be reduced to an acceptable level. The field monitoring results show that the maximum wall deflection near the historical building was 23 mm. At the site boundary near the tunnels, the maximum displacement of the walls was 30.7 mm. The earth pressures and pore water pressure at the active side were reduced gradually during the excavation