Optimizing Cutterhead Scouring Systems for Large‐Diameter Slurry Shields: A Case Study of the Qingdao Second Submarine Tunnel

Frequent occurrences of shield clogging during slurry shield tunneling emphasize the necessity of optimizing cutterhead scouring systems. Conventional studies largely rely on empirical design and simplified analyses, which fail to capture complex flow–solid interactions or enable quantitative optimization. To overcome these limitations, a computational fluid dynamics (CFD) model was developed to simulate jet flow formation in shield nozzles and the flow field in the cutterhead excavation zone. It allows to systematically investigate the effects of nozzle inlet velocity, slurry chamber pressure, and cutterhead rotation speed, promoting the optimization of nozzle geometry and arrangement. The optimized configuration has been validated in the Qingdao Second Submarine Tunnel. Results show that increasing inlet velocity enhances jet strength without altering the overall velocity distribution pattern. Cutterhead rotation generates a rotating flow field that intensifies scouring but causes jet deflection, while interference between central and adjacent nozzles limits the effective scouring area. By modifying the outlet geometry and eliminating ineffective main arm nozzles, both the effective scouring area ratio and scouring efficiency index were improved. The optimized configuration ensures stable and efficient advancement when the nozzle inlet velocity exceeds 4 m/s, effectively preventing shield clogging. This work provides a validated modeling framework and practical optimization strategy for enhancing slurry shield performance in complex geological conditions.