【作者】 卢慈荣；

【导师】 蒋建群；

【作者基本信息】 浙江大学 ， 水工结构工程， 2005， 硕士

【摘要】 盾构法隧道是现代都市生命线工程的重要组成部分，因此其地震安全性的研究具有极其重要的社会、政治和经济意义。本文重点研究了盾构法隧道纵向地震响应与抗震设计方面的问题，根据震害分析可将研究内容分为两个方面。一是盾构法隧道结构在地震行波作用下的动力响应分析与抗震设计，二是盾构法隧道在不均匀震陷下的纵向受力研究与抗震设计。 盾构法隧道由于其自身构造的复杂性，分析中首先要解决计算模型的建立问题，对比考虑各种现有模型后，本文选取了日本志波由纪夫等人提出的等价连续化模型，该模型可以避免对盾构法隧道结构的衬砌管片与纵向连接螺栓各自建模后所带来的接头单元刚度难以理论分析的问题。按该模型可将隧道视为粘弹塑性地基上的连续梁，土与结构之间的相互作用可用非线性弹簧和阻尼来模拟。针对目前模型的等价单元刚度计算中未能考虑轴向力与弯矩共同作用，在充分考虑螺栓非线性受力特性的基础上，本文首次推导出轴向力与弯矩同时作用场合非线性等价单元刚度的完备计算式。在此基础上针对地震行波和不均匀震陷，分别采用非线性动力有限元法和反应变位法编制相关分析程序；研究了中强震行波作用下盾构法隧道的纵向响应特性及相关抗震设计要点；分析了盾构法隧道在不均匀震陷下的纵向受力特性；并探讨了地基与隧道各构成要素对隧道纵向地震响应的影响以及螺栓非线性、不均匀震陷范围、地基刚度折减系数、隧道与其他构造物连接方式、震陷模式等要素对盾构法隧道在不均匀震陷下的纵向受力影响规律。通过算例分析，得出以下结论： 1．地震动作用下纵向螺栓搭接处往往成为盾构法隧道破损的薄弱环节，地下隧道结构抗震设计的原则不应该是抵抗周边土体的运动，而应该是将隧道设计成可适应其运动变位的柔性结构。 2．盾构法隧道结构的纵向抗震设计建议采用螺栓最大张开量作为设计的控制指标。同时，塑性比指标可较为直观地了解纵向连接截面上螺栓的受力情况。 3．采用等价连续化模型进行盾构法隧道的纵向受力分析时，等价弯曲刚度计算不考虑轴向力所得结果与实际有较大差异。因此，采用等价连续化模型进行盾构法隧道纵向受力分析时，在单元等价弯曲刚度计算中计入轴向作用力的影响是十分必要的。 4．行波作用时，在正常使用工况下反应变位法仍不失为简便实用的分析方法，但在螺栓进入塑性受力阶段后该法所得螺栓最大张开量就偏小了，此时就不得不借助于非线性动力有限元法进行隧道的纵向抗震分析。在中强震作用下，有必要考虑螺栓的非线性，同时螺栓强度的适当提高与预应力的施加有助于提高隧道的纵向受力性能，特别是螺栓预应力的施加，工程实践中无疑应尽可能采用。管片尺寸对隧道纵向抗震设计的影响相对较少，但从有利于接头受力与降低工程造价角度出发，适当降低管片厚度是合理的。而管片环宽的增大虽然给施工带来便利，但考虑到这会导致纵向连接螺栓易于进入塑性受力状态，故环宽的加大宜结合多方面因素慎重考虑。在发生不均匀震陷时，不均匀震陷范围、地基刚度折减系数、隧道与其他构造物连接方式及震陷模式对盾构法隧道的纵向受力影响较大，尤其是震陷模式宜根据具体的场地条件进行专门分析，隧道与其他构造物连接方式宜采用柔性连接。 本文通过对盾构法隧道纵向响应特性的分析，得出各要素对其响应的影响规律，所得结论可为实际工程中盾构法隧道的初步设计提供有益的参考，同时所编制分析程序也可用于盾构法隧道在长期荷载作用下产生永久地基变形时的纵向受力分析与安全性验算。关键词:盾构法隧道纵向连接螺栓纵向地震响应等价连续化模型行波不均匀震陷非线性动力有限元共同作用更多还原

【Abstract】 Shield tunnel is one of the important lifeline engineering, so the research on its seismic security has the important social, politics and economic significance. In this dissertation, the problem of longitudinal seismic response and seismic design are considered. Field observations showed that there are two major causes to shield tunnel during ground shaking: earthquake wave propagation and differential subsidence due to earthquake. These aspects will be analyzed individually in this paper.In the research, the first and prime problem is how to model this specific discontinuous structure of shield tunnel, because shield tunnel is constructed with a lot of segments that are connected with the join bolts. In this dissertation, equivalent uniform model, which is advised by Japanese scholar, is adopted. Then shield tunnel is modeled as a uniform beam supported on the viscoelastic foundation of Winkler type. This model can avoid the problem that how to calculate the stiffness of longitudinal join bolts theoretically, which should be determined though model test. The nonlinear equivalent stiffness formula, considering the coactions of axial force and bending moment, is derived firstly. The nonlinear dynamic FEM program for analyzing the longitudinal response of shield tunnel subjected to earthquake wave propagation and differential subsidence due to earthquake. Stretch value of bolt is suggested as guideposts in design. Such aspects as equivalent rigidity, foundation parameter, domain and pattern of subsidence, reduced subgrade rigidity and non-linearity of bolt are discussed in detail. Some conclusions are obtained through analyses results.1. Longitudinal bolts always are weak links of shield tunnel. The aseismic design principle of substructure is how to adapt the deformation of circumference soil body.2. Maximal stretch value of bolt is suggested as guideposts in design, and plasticity ratio can favorably predominate plastic stress of bolts.3. It’s necessary to considerate the axial force and bending moment coactions in the calculation of equivalent rigidity.4. In normal work condition, seismic deformation method is a simple practical method under traveling wave, but maximal stretch value of bolt will be too little instrong earthquake. Then nonlinear dynamic FEM have to be adopted.5. It’s necessary to considerate the non-linearity of bolt in strong earthquake. High strength friction grip bolt and application of initial stress are propitious to enhance the earthquake resistance of shield tunnel.6. The thickness of segment should be lowest possibly, and increasing the width of segment-ring is unfavorable to enhance the earthquake resistance of shield tunnel. So it should be special approved.7. Such aspects of joint fashion, reduced subgrade rigidity, domain and pattern of subsidence is important to the earthquake resistance of shield tunnel. Some parameters have to be determined through special analyses in practice.Through the research on the longitudinal nonlinear dynamic response of shield tunnel due to earthquake, and the influence of some correlative parameters on the response, providing an academic foundation for seismic design code recension of shield tunnel and upgrading its seismic design. The methods and programs developed in this dissertation can also be used in analyzing the internal force of shield tunnel uneven ground settlement due to long-period load.更多还原