Abstract: This paper presents a case history of the impact of the closely deep excavation on the surrounding the existing subway viaduct piles. In the underground transfer center project at the proposed Suzhou Metro Line No. 8 and the existing Line No. 2, a three-dimensional finite element simulation numerical model was used to study the impact of different excavation sequences and soil reinforcement lengths on the safety of the existing bridge piles of the surrounding deep excavations. The numerical results are compared with the field monitoring data. The evaluation results show that the symmetrical synchronous excavation of the proposed foundations on both sides of bridge piles has less surrounding surface settlement, the less deformation of the retaining structure and the less deformation of viaduct piles than that of the sequential excavation. The ability of the soil surrounding the pile to resist deformation increases with the increase of the reinforcement length of the protective casing. When the reinforcement length exceeds the excavation depth, the improvement effect of the ability of the soil around the pile to resist deformation is no longer obvious, and the optimal reinforcement length of the bridge pile is basically the same as the excavation depth.

Key words: Deep Excavation, Subway, Bridge Piles, Numerical Simulation, Field Tests