Deformation of metro station excavation and its influence on nearby pile foundations of bridge

A three-dimensional explicit finite difference simulation is carried out to investigate the deformation of a metro station excavation and its influence on the nearby embedded pile foundations in combination with an underground metro station project in Shanghai soft soil deposits, which is under-crossing an urban elevated bridge and adjacent to its pile foundations. The numerical model, taking account of the interaction among the soil, retaining structures and nearby pile foundations, is established based on the geotechnical program FLAC3D, and the modified Cam-clay constitutive model is adopted to describe the deformation behavior of the soil. The computed lateral displacement curves of the retaining wall agree well with those of the in-situ measurements. This indicates that it is feasible to use the numerical model to predict the performance of the embedded piles underlying the abutment, which can not be monitored at the site. The parametric analysis and the comparison with the other relevant excavation projects show that the adopted countermeasures, which include adjustment of retaining structure scheme, inside ground reclamation and pre-installation of local concrete slab, not only restrict the deformation of the excavation itself effectively, but also protect the safety of the pile foundations as well as the upper bridge appropriately.