Comparative analysis of influences of different deformation modes of retaining structures on deformation of existing tunnels outside excavations

As more and more subways have been constructed and put into operation, control of the influences of the adjacent excavation on the existing tunnels becomes more and more important. Both the deformation characteristics of the existing tunnels at different locations and the influenced range of displacement caused by four deformation modes of retaining structures are analyzed through FEM modeling. The results show that under the situations of different deformation modes of retaining structures with the same maximal horizontal displacement, the deformations of the existing tunnels outside the excavations can be considerably different. According to the vertical deformation characteristics of the vault and invert of the tunnel, the soil layer outside the excavation can be divided into three zones, i.e., settlement zone, transition zone and heave zone. The effect zone on the deformation of the existing tunnel caused by the cantilever deformation of retaining structures is the smallest; for the convex and composite deformation modes, the ranges are similar and their distribution is larger than that of the cantilever deformation mode; the influenced range caused by the kick-in deformation mode is the largest among these four modes. In practice, besides controlling the maximum horizontal displacements of the retaining structures, the deformation mode of the retaining structures should also be optimized according to the surrounding environment, and the kick-in deformation of the retaining structures should be avoided.