Influence of deep excavation on deformation of operating metro tunnels and countermeasures

According to the practice of deep excavation adjacent to the subway tunnel in Shanghai, the software FLAC-3D is employed to establish a numerical model to simulate the whole dynamic process of the deep excavation. The calculated results show good agreement with the field measurements. The two results show that deep excavation adjacent to the operating metro tunnel at its one side induces uneven deformation. In order to protect the adjacent existing tunnel, a construction technology of the two-time reinforcement outside the deep excavation is brought forward and adopted. Underground obstacle as the barrier against the displacement transfer induced by deep excavation is presented for the first time. Different construction methods are simulated by the numerical method. The results indicate that the two-time reinforcement outside the deep excavation and the reversed construction method can effectively control the deformation of the metro tunnel.