Abstract: The foundation excavation above the tunnel structures will change the stress field due to the unloading of soils and disturb the adjacent soils surround the excavated area. Therefore, the tunnel structure might be adversely affected by the construction above. This paper proposes the optimized deep excavation method and sequences that can ensure the safety of the tunnel structure as well as the operation safety. Both the analysis and construction monitoring results indicate that the appropriate soil improvement at the bottom, utilizing the uplift piles, slabs that can resist the buoyancy, appropriate layered and zone excavation are the effective ways to control the deformation of the underlying tunnel. During the excavation, it is also important to select the construction method that having minimal impact to the adjacent environment and to utilize the informational construction methods that providing realtime feed back to the proposed construction.

Key words: Metro Tunnel, Foundation Excavation, Tunnel Deformation, Protective Measures