甬江沉管隧道长期沉降监测数据及有限元分析

甬江沉管隧道位于甬江下游河湾处的软土地基上，地基承载力较低，使隧道发生了较大的沉降。此外，甬江严重的淤积及每天2.67 m的潮差对隧道的沉降产生了显著的影响。依据甬江沉管隧道运营期间16 a的沉降监测数据，结合地层条件、潮汐和清淤资料，对该条沉管隧道的长期沉降进行了分析，并提出了基于流-固耦合理论的有限元方法计算沉管隧道的长期沉降，计算结果与监测结果具有较好的一致性。此外，采用上述计算方法分析了影响沉管隧道沉降的3个主要因素（即地层条件、基槽淤积和回淤与清淤）对隧道运营期沉降的影响。分析表明，地层条件是影响沉管隧道沉降的主要因素，软土地基隧道沉降远大于其他地基。潮汐作用会使隧道沉降发生周期性变化，该变化约占隧道运营期沉降的4%～10%。淤积对隧道长期沉降影响显著，但定期清淤只能短时间减小隧道的沉降，使隧道沉降产生周期性变化。上述结论均可为相关工程提供参考。

Monitoring data and finite element analysis of long term settlement of Yongjiang immersed tunnel

Yongjiang immersed tunnel, built in 1987 and opened in 1995, is a 420 m long road immersed tunnel. It is on the soft soil foundation in a bend of Yongjiang River, which has caused large settlement. Moreover, the severe sediment deposition and 2.67m tidal range in Yongjiang River also have a great influence on the settlement of tunnel. Based on the monitoring data of settlement, the paper analyses the subsoil conditions, tide and desilting’s influence on settlement. And a finite element method based on fluid-solid coupling method is put forward to simulate the long term settlement, and the simulation results are in good agreement with the monitoring data. In addition, the key influencing factors of tunnel settlement, including subsoil condition, trench siltation and siltation and desilting above the element, are calculated and compared. The monitoring data and finite element analysis show that the subsoil condition is the main factor that determines the magnitude of settlement, and the settlement of tunnel on soft soil is much larger than that on other kind of foundations; because of the tidal range, tunnel is subject to an oscillation of elevation which may account for 4%~10% of settlement of operation period; the effect of silting on tunnel is obvious, but regular desilting can only decrease the settlement temporarily and cause the settlement cyclic variation. Although the monitoring data were obtained from a specific project, the conclusions of the study are sufficiently general and may apply in other immersed tunneling projects.