Study on disturbance mechanism of complex cross-section construction in shallow buried excavation tunnel crossing sections on strata and pipelines – A case study of Beijing metro line 12

This study investigates the disturbance effects of complex cross-section tunnel construction on strata and pipelines based on the crossing section project in Beijing Metro Line 12. A finite element numerical model was established to simulate the excavation of large cross-section tunnel under six parallel municipal pipelines. The excavation process was simulated in accordance with actual construction steps, and the model validity was verified using field monitoring data. Through systematic field monitoring, the influence patterns of variable cross-section tunnel construction on strata and adjacent pipeline settlement were analyzed. Results show that: settlement induced by construction exhibits significant double-line superposition effects, with later excavated tunnels contributing more prominently to strata and pipeline settlement; the larger the cross-section size and the smaller the tunnel wall spacing, the greater the strata settlement induced by construction; pipeline settlement is mainly controlled by its horizontal distance from the tunnel, with closer distances resulting in more significant settlement. The study demonstrates that grouting pre-reinforcement and lifting measures at key cross-section positions can effectively suppress settlement development and promote its rebound. This research reveals the disturbance patterns of strata and pipelines under cross-section tunnel construction, providing important technical references for construction optimisation in similar projects.