软土盾构隧道施工阶段上浮计算模型探讨

Calculation Model of the Uplift Movement of a Shield Tunnel during Construction in Soft Soil

  • 摘要: 文章首先对管片上浮作用机理进行了分析,确定了盾构隧道施工阶段上浮计算模型荷载分布规律和计算方法;其次指出了弹性支撑法和修正惯用法直接运用于盾构隧道上浮阶段设计所存在的问题,即弹性支撑法计算得到管片底部向下位移,与实际上浮阶段管片隆起不符,而修正惯用法又不能考虑拱顶上覆土体反向压缩特性;最后,基于弹性支撑法并利用修正惯用法思想提出了能规避上述两个问题的反转抗力力学模型。结果表明:提出的计算模型与施工阶段管片上浮变形特征吻合度高,施工阶段管片上浮状态下弯矩、轴力和剪力最值较弹性支撑法和修正惯用法获得的结果分别增加 68%、21%和 51%以及 34%、69%和 22%,说明按本文推荐计算模型进行上浮管片设计可避免实际工程配筋不足造成的管片破损、开裂或渗漏。其结论可为盾构隧道设计提供一定理论支撑和参考。

     

    Abstract: The uplift mechanism of a segment is analyzed, and the load distribution law of a calculation model for segment uplift during shield tunnel construction is determined. There are some problems if the elastic support method and modified routine method are directly applied to the design of a shield tunnel during uplifting: calculations by the elastic support method show that segment bottom moves downward and doesn′t conform to the actual conditions of segment uplift, while the modified routine method doesn′t consider the reverse compress characteristics of the overflying soil mass at the tunnel crown. Based on the elastic support method and thoughts of a modified routine method, a mechanical model of reversal resistance is set up. The results show the proposed calculation model agrees very well with the characteristics of segment uplift during construction. The maximum and minimum values of the bending moment, axial force and shear force under the state of segment uplift during construction increase by 68%,21%, 51%, and 34%, 69%, 22%, respectively, compared with the elastic support method and modified routine method, which shows that segment damage and cracking or leaking caused by inadequate reinforcement can be avoided with the proposed design method for an uplift segment.

     

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