应变软化模型在浅埋土质隧道数值模拟中的应用

发布时间：2018-05-17 01:04

本文选题：浅埋隧道 + 数值模拟　；参考：《华中科技大学》2014年硕士论文

【摘要】：在浅埋土质隧道掘进过程中，当土体变形达到一定程度后，由于土体的应变软化特性，土体强度明显降低，从而使得隧道易发生失稳、冒顶、坍塌等现象。因此，土体的应变软化特性对浅埋土质隧道的稳定性易造成不利影响。然而，目前大多数关于浅埋土质隧道的研究并未考虑土体应变软化特性。针对以上问题，本文采用FLAC3D建立三维数值仿真模型，在模拟隧道开挖过程中考虑土体的应变软化特性，以探究其对浅埋土质隧道的稳定性影响。首先，介绍了FLAC3D中应变软化模型的相关理论，并结合直剪试验，明确开挖现场土体应变软化的相关参数。基于现场监控量测数据，确定在三维仿真模型中土体开挖时、初期支护施加时、二衬施加时对应的应力释放率。其次，，采用FLAC3D中内嵌的摩尔-库伦应变软化模型和摩尔-库伦理想弹塑性模型分别对隧道施工过程进行模拟，结果表明：与理想弹塑性模型相比，采用应变软化模型计算得到的隧道土体变形、掌子面内空位移以及土体塑性区范围都明显较大。因此，忽略土体应变软化特性的浅埋土质隧道设计偏于危险。最后，对FLAC3D中应变软化模型的相关参数（强度折减率、临界塑性软化系数）引起的隧道开挖的力学响应进行分析，结果表明：隧道土体变形、掌子面内空位移以及土体塑性区范围均随强度折减率或临界塑性软化系数的减小而增大，且强度折减率对其影响更大。本文的研究成果可为浅埋土质隧道的设计与施工提供有益的参考。
[Abstract]:In the tunneling process of shallow buried soil tunnel, when the deformation of soil reaches a certain degree, the strength of soil decreases obviously due to the strain softening characteristics of soil, which makes the tunnel prone to instability, roof fall, collapse and other phenomena. Therefore, the strain softening property of soil easily affects the stability of shallow soil tunnel. However, most researches on shallow-buried soil tunnels do not take strain softening into account. To solve the above problems, a three-dimensional numerical simulation model is established by using FLAC3D to simulate the strain softening characteristics of soil in the process of tunnel excavation, so as to explore its influence on the stability of shallow buried soil tunnel. Firstly, the theory of strain softening model in FLAC3D is introduced, and the related parameters of soil strain softening in excavation site are determined by direct shear test. Based on the field monitoring data, the stress release rate is determined when the soil is excavated in the three-dimensional simulation model, when the initial support is applied, and when the second lining is applied. Secondly, the Mole-Coulomb strain softening model and the Moor-Coulomb ideal elastic-plastic model embedded in FLAC3D are used to simulate the tunnel construction process respectively. The results show that compared with the ideal elastic-plastic model, The strain softening model is used to calculate the deformation of tunnel soil, the displacement in the face of the tunnel and the plastic zone of the soil are obviously larger. Therefore, the design of shallow soil tunnel which neglects the strain softening characteristics of soil is dangerous. Finally, the mechanical response of tunnel excavation caused by the parameters of strain softening model (strength reduction rate, critical plastic softening coefficient) in FLAC3D is analyzed. The void displacement and the range of soil plastic zone increase with the decrease of strength reduction rate or critical plastic softening coefficient, and the strength reduction rate has more influence on it. The research results of this paper can provide a useful reference for the design and construction of shallow-buried soil tunnel.
【学位授予单位】：华中科技大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U452.11

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