Objective Segment misalignment during downhill shield tunneling in water-rich soft soil strata is a high-risk factor in shield construction, as such misalignment can seriously affect construction safety and progress. At present, related studies have not specifically addressed segment misalignment in downhill shield tunneling under water-rich soft soil conditions; therefore, it is necessary to conduct targeted research on the influencing factors of segment misalignment in this type of stratum.

Method From a theoretical perspective, the severe consequences of segment misalignment, including water leakage, grout leakage, and segment damage, are analyzed. The specific causes of segment misalignment are examined in detail from two aspects: misalignment control standards and on-site operations. This provides theoretical support for technical measures to control segment misalignment in downhill shield tunneling in water-rich soft soil stratum.

Result & Conclusion  After adopting the proposed segment misalignment control measures, the elevation difference between individual segments from the start of segment assembly to shield tail clearance in the case tunnel is controlled within 2 mm, and the misalignment between adjacent segments is controlled within 4 mm. After the segments exited the shield tail and until tunnel formation, the misalignment within the same ring is controlled within 12 mm, and the misalignment between adjacent segments is controlled within 17 mm. The results indicate that by reasonably optimizing segment assembly positions and properly controlling excavation parameters and synchronous grouting materials, segment misalignment in downhill shield tunneling in water-rich soft soil strata can be controlled to meet specification requirements.