Case study and treatment technology for deformed shield tunnel in soft soils induced by road construction

With the gradual improvement of urban rail transit network and the development of urbanization in China, the loading and unloading conditions near the metro tunnels are becoming more and more frequent, which seriously threaten the safety of the lining structures and their serviceability. A field case of deformed shield tunnel in Shanghai caused by road construction is introduced. The transverse deformation of the tunnel is very large, which is 159 mm (i.e., 25.6‰ D, D is the tunnel diameter), resulting in serious structural damage, such as water leakage, mud leakage, joint opening, etc. The details of the field case are comprehensively recorded, including engineering geological data, road construction, tunnel deformation forms and subsequent deformation treatment measures, and a quantitative analysis is made on the treatment effects, especially the repair effects of lateral small disturbance grouting technology. According to the monitoring and inspection data, it is found that the convergence deformation caused by road construction is about 30~50 mm, which can be exacerbated by the river backfilling. The soil grouting at the both sides of the tunnel spring line can reduce tunnel convergence effectively, and the effectiveness is closely related to the magnitude of tunnel convergence before grouting. The installation of steel plates can improve the bearing capacity of tunnel lining ring so as to ensure the road construction and the safety of the tunnel.