Numerical simulation of segment floating in shield tunnel construction using coupled IBM–FVM

Segment floating, often induced by simultaneous grouting during shield tunnel construction, poses significant challenges. This paper introduces a novel fluid–solid interaction (FSI) numerical method that integrates the immersed boundary method (IBM) and finite volume method (FVM) to simulate the buoyancy-driven floating of segments in shield tunneling accurately. The IBM effectively models the interaction between the segment and the slurry, while the governing equations are discretized using the FVM on a uniform orthogonal collocated grid. The proposed method was validated using field data from two engineering cases. For Hangzhou Metro Line 7, the relative errors between the simulated and measured segment floating displacements at critical time intervals (2–10 h) were within ± 0.2%. For the Sofia Tunnel, the average absolute errors between the simulated and measured slurry pressures were 0.01–0.07 bar at the selected monitoring points and times. These results confirm the accuracy of the method in simulating rapid segment floating dynamics and real-time slurry flow behavior during shield tunnel construction. By emphasizing the key role of the FSI in addressing the complex interactions between the fluid and solid phases, this study advances the simulation of segment floating during shield tunnel construction.