新建盾构隧道施工对近接平行隧道的影响分析

针对软土地层中浅埋大直径盾构隧道施工对既有近距离平行隧道的影响,以上海人民路越江隧道工程为背景,采用三维有限差分数值分析方法对南线隧道施工引起北线隧道的变形和洞周土压力的变化规律进行了研究。数值模拟结果表明新建隧道施工会使既有隧道侧向受压,引起既有隧道拱腰部位产生较大的压缩变形,拱顶及仰拱部位产生较大的张拉变形。新建隧道掘进过程中,既有隧道周围土压力经历增加、减小和趋于稳定三个状态。将数值计算结果与现场实测资料进行对比分析,表明计算值与实测值基本一致。此外,数值计算还有效弥补了现场实测在土体位移分布和土体塑性区形成方面的不足,计算结果表明受新建隧道施工影响,既有隧道周围地层位移和塑性区范围都有增加。研究结果可以为浅埋大直径近距离越江盾构隧道的设计和施工提供参考。

Analysis on Influence of New Shield Tunneling on Closely Spaced Parallel Tunnel

In order to study the influence of shallow-covered and large diameter shield tunnel construction on the existing parallel tunnel in soft ground, with the Renmin road river-crossing tunnel in Shanghai as background, a 3D finite difference numerical analysis is adopted to the research on the influence of south line shield tunnel construction on the built north line. The deformations of existing tunnel and soil pressure around it resulted from the new parallel tunnel construction are investigated. The results show that the existing tunnel was under lateral extrusion during the parallel tunnel excavation, and great compression deformation occurred at the spring line and tensile deformation appeared at the crown and invert of the existing tunnel. The soil pressure around the existing tunnel experienced a sequence of increasing, decreasing and stabilizing states during the parallel tunneling. These results of the numerical analysis are qualitatively fit well with in-situ measurements. Furthermore, the numerical simulation compensates drawbacks of in-situ monitoring in distribution of ground movements and developments of soil plastic zone during new tunnel construction. It shows that there was growth of vertical settlement of subsurface ground and plastic zone around existing tunnel during new parallel tunnel excavation. Such findings can serve as references for the design and construction of river-crossing shield tunnel characterized by shallow-covering, large diameter and close spacing.