Design and field measurement of excavation on operating metro tunnels

Based on the foundation pit of a box tunnel crossing over operating metro tunnels, the form of supporting structure and the excavating mode are designed. The finite element analysis and measured results show that the method to use artificial strip-slope excavation and board-anchor supporting structures to restrict the rebound of bottom soils and the deformation of the operating metro tunnels are very effective. The method considers the time-space effect of excavation. The artificial strip-slope excavation is mainly used to control the rebound of bottom soils and to restrict the floating of tunnels during excavation. The board-anchor supporting structure is used to restrict the deformation of the tunnels due to the soil unloading after excavation. This project adopts the finite element numerical analysis method to forecast the deformation before construction and the automatic monitoring method to instruct construction. The successful experience of this project may provide valuable reference for the similar projects.