双地层盾构隧道开挖面稳定性研究

发布时间：2018-06-28 11:22

本文选题：盾构隧道 + 开挖面　；参考：《湖南大学》2014年硕士论文

【摘要】：盾构法是隧道暗挖法中的一种全机械化的施工方法。它以对周围环境影响小、机械化程度高及隧洞成型质量好等优点而被广泛应用。盾构隧道施工中，选择合理的开挖面支护力，不仅能够保证开挖面的稳定，，而且能够有效减少开挖对周围地层变位及构筑物的影响。当盾构机通过软硬不均的双地层时，上地层软土和下卧硬层的刚度差异较大，导致开挖面支护压力比在均质土层中更加难以控制。如控制不当，会造成地表沉降过大甚至发生工程事故。因此，进行双地层条件下盾构隧道开挖面稳定性研究具有重要理论和工程意义。本文拟对盾构隧道在双地层条件下的稳定性进行了数值模拟和理论分析，主要内容如下：首先，选用非线性软件ADINA进行数值模拟分析。通过设计模拟方案与已有文献进行对比，验证此软件在分析隧道开挖问题上的可行性。分别建立上软下硬土层和上硬下软土层条件的隧道开挖模型，通过依次减小开挖面支护力，得到相应的开挖面中心点水平位移及对应的地表沉降。通过分析中心点的水平位移随开挖面支护力变化的规律求得极限最小支护力。比较这两种地质条件下隧道失稳的破坏形式，为理论模型的建立提供依据。对隧道进行敏感性参数分析，讨论埋深、上层土体弹性模量及上层土体内摩擦角对开挖面极限支护力的影响。其次，对已有楔形体模型进行归纳总结，基于极限平衡理论及数值分析的结论提出适用于双地层的楔形体模型，通过平衡方程求解出极限支护力的表达式。将上述模型拓展到复杂地层开挖面支护力的分析，给出用于分析复杂地层开挖面支护力公式。当上部土层为软弱土层时，滑动面的底边可能出现在两土层的交界线处，而不是隧道的底部，开挖面发生部分失稳破坏。最后，结合广州地铁某施工段的实际情况进行数值模拟和理论模型分析，所得的结果与工程实测结果相近，证明本文的数值模拟方法与理论模型可行，能够用于分析工程问题。
[Abstract]:Shield tunneling is a fully mechanized construction method in tunneling. It is widely used because of its small influence on the surrounding environment, high degree of mechanization and good quality of tunnel forming. In shield tunnel construction, choosing reasonable excavation surface support force can not only guarantee the stability of excavation surface, but also effectively reduce the influence of excavation on surrounding strata displacement and structure. When the shield machine passes through the hard and soft double strata, the stiffness difference between the upper soft soil and the underlying hard layer is great, which results in more difficult to control the support pressure of the excavated surface than in the homogeneous soil layer. If the control is not proper, it will cause the surface subsidence to be too large or even an engineering accident. Therefore, it is of great theoretical and engineering significance to study the excavation surface stability of shield tunnel under double strata. In this paper, numerical simulation and theoretical analysis of the stability of shield tunnel under the condition of double strata are carried out. The main contents are as follows: firstly, the nonlinear software Adina is used to carry out the numerical simulation and analysis. The feasibility of the software in the analysis of tunnel excavation problem is verified by comparing the design simulation scheme with the existing literature. The tunnel excavation models of the upper soft and lower hard soil layer and the upper and lower soft soil layer are established respectively. The horizontal displacement of the center point of the excavated surface and the corresponding surface settlement are obtained by decreasing the supporting force of the excavated surface in turn. The limit minimum support force is obtained by analyzing the law of horizontal displacement of center point changing with the support force of excavating surface. The failure modes of tunnel instability under these two geological conditions are compared to provide the basis for the establishment of theoretical model. The sensitivity parameters of the tunnel are analyzed, and the effects of the depth of the tunnel, the elastic modulus of the upper soil and the internal friction angle of the upper soil on the ultimate support force of the excavated surface are discussed. Secondly, the existing wedge model is summarized. Based on the limit equilibrium theory and numerical analysis, the wedge-shaped model suitable for the double strata is proposed, and the expression of the ultimate support force is solved by the equilibrium equation. The above model is extended to the analysis of the support force of the excavated surface in complex strata, and the formula for analyzing the support force of the excavated surface in the complex formation is given. When the upper soil layer is a weak soil layer, the bottom of the sliding surface may appear at the junction of the two soil layers rather than the bottom of the tunnel. Finally, the numerical simulation and theoretical model analysis are carried out according to the actual situation of a certain construction section of Guangzhou Metro. The results obtained are similar to the measured results, which proves that the numerical simulation method and the theoretical model in this paper are feasible and can be used in the analysis of engineering problems.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U455.43

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