Numerical Analysis of Shield Tunnel Driving underneath an Existing Railway and Related Reinforcement Effects on Subsidence Control

Through a two-dimensional, finite element numerical method, and with the help of Plaxis software, a shield tunnel of power cable driving under the existing railway line was simulated. To protect the railway from the excessive subsidence caused by tunneling, the effects of three grouting reinforcement schemes, differing in grouting range, were analyzed. Scheme I reinforced soils above the tunnel, scheme II was half-section reinforcement, and scheme III was full-section reinforcement. The results showed that all three schemes could meet the requirement of subsidence control. However, compared with the two other schemes. scheme III had engineering feasibility, could help reduce bending moment of the segment, and would benefit the long-term stability of tunnels. In all, the full-section reinforcement was recommended.