宁波地铁盾构施工对邻近高架桥梁基础的影响

Influence of Shielded Transit Construction on Adjacent Viaduct Foundations in Ningbo Soft Soils

盾构施工对既有桥梁的影响是一个非常突出的问题。以宁波地铁8号线盾构区间下穿城市高架桥梁为依托,借助MIDAS GTS NX三维有限元软件,建立相应的盾构施工模型,分析盾构施工对宁波地区高架桥墩顶的变形影响。结果表明:盾构施工过程,桥墩顶水平位移(横桥向、顺桥向)均先增大后减小再增大,表现为双峰曲线,且前者的峰值时刻要早于后者,而竖向位移(隆起、沉降)均不断增大,接近于线性曲线。根据数值计算得到的桥墩顶位移结果,提出相对应的位移控制指标,并结合盾构施工期间高架桥墩位移监测数据,验证了上述控制指标的可行性及合理性,可供宁波及类似地区盾构隧道工程借鉴。

The influence of shielded transit tunnel construction on the existing bridge foundations is a very prominent issue.This paper presents a case history of on the shielded section of Ningbo Metro Line 8 under crossing the urban viaduct.The cor-responding shielded tunnel construction model is established by using the Midas GTS NX 3D finite element software to analyze the deformation at the top of a viaduct pier.The results indicate that,during the shield construction process,the horizontal displacement(transverse and longitudinal)at the top of the bridge pier first increases,then decreases,and then increases,which exhibiting a bimodal curve.The peak moment of the former is earlier than that of the latter.While the vertical displace-ment(upheave and settlement)continuously increases,approaching a linear curve.According to the displacement results of the pier top obtained by the numerical analysis,the corresponding displacement control indies are recommended.The feasibility and rationality of the above control indicators are verified by combining with the displacement monitoring data of the viaduct pier during shielded transit tunnel construction,which can provide a reference for the similar shielded tunnel excavation projects in Ningboareas.