Soil Dynamic Stress of a Transition Zone Influenced by the Shield Tunnel Beneath a Railroad

Uneven settlement and variation in track stiffness are inherent issues of culvert–embankment transition zones. Therefore, the construction of a shield tunnel (a temporary support structure for tunnel construction) in the vicinity of a transition zone may aggravate track geometry deterioration, increase maintenance demand, and cause poor ride quality. This study investigated the influence of shield tunnel construction on the distribution of soil dynamic stress. A construction project of shield tunnels for a metro line beneath an existing railroad was employed as a case study. A plane strain model that was realized by the finite element analysis method was employed to investigate the distribution discipline of the soil dynamic stress in transition zones, which was induced by the passing train and the shield tunnel beneath the railway. The results indicate that the existence of a shield tunnel structure will increase the soil dynamic stress in the transition zone. Because of the tunnel structure, the soil dynamic stress is 38% greater than the soil dynamic stress in the case without a tunnel at a depth of 16 m. Consequently, a recommended treatment is introduced according to the properties of the surrounding soil. Numerical simulation revealed that this treatment is appropriate for reducing the soil dynamic stress in a transition zone.