【作者】 李辉；

【导师】 郑余朝；

【作者基本信息】 西南交通大学 ， 桥梁与隧道工程， 2014， 硕士

【摘要】 对于在既有地铁盾构隧道旁采用桩锚技术施工的大型基坑工程,由于基坑的大面积开挖卸荷打破了原有的地层平衡条件,使得基坑周围土体在不平衡力的作用下向着基坑方向变形和位移,同时这种不平衡作用改变了既有盾构隧道周边围岩应力状态,导致围岩应力出现应力重分布,而既有盾构隧道是根据原先的围岩条件设计而成,再者地铁盾构隧道对岩土体变形比较敏感,极易由于岩土的变形而出现不均匀位移,当基坑开挖的卸荷影响达到一定程度,就会威胁到盾构隧道的正常使用和结构安全,如轨道线形不满足列车运营要求,盾构接头螺栓出现拉伸破坏,管片接头防水措施失效,盾构管片出现纵向错动等现象的产生。那么在基坑开挖的一个多大范围之内,基坑开挖对邻近既有盾构隧道影响比较强烈,必须采取施工对策才能保证盾构隧道的正常使用和基坑的顺利施工；在什么范围内基坑开挖对邻近既有盾构隧道影响比较弱甚至没有影响,只需采用一般的施工辅助措施甚至不需要采取施工对策,这是摆在广大学者和岩土工程师面前亟待解决的一个问题。本文以沈阳中环广场南块地超大基坑近接既有地铁盾构隧道施工工程为背景,在对盾构隧道纵向等效刚度模型进行研究分析的基础上确定将盾构隧道纵向变形曲率作为近接影响分区准则,然后利用大型有限元软件Abaqus,通过改变既有盾构和基坑围护结构之间的距离,对既有盾构隧道位于基坑侧方、基坑底面-45°方向、基坑被动土区、基坑底面正下方4种类型12种工况进行三维数值模拟,分析基坑开挖对地表沉降变形,既有盾构隧道变形和连续墙水平变形的影响规律,主要结论及成果如下：(1)通过对盾构隧道纵向等效刚度模型的研究,表明盾构隧道纵向变形曲率半径和螺栓张开量与螺栓内力之间存在着力学和数学上的关系,也是基坑近接盾构隧道施工中隧道结构安全和正常使用的关键指标,从而确定将盾构隧道纵向变形曲率半径作为近接影响判断准则。(2)将盾构隧道轨道线形是否受到影响的临界状态、盾构隧道管片环间接头处于极限状态对应的盾构隧道纵向变形曲率半径分别作为强弱影响区和弱无影响区的划分阈值,然后在数值模拟分析的基础上建立基于桩锚技术的基坑近接既有盾构隧道施工工程的影响分区图,并提出了相应的施工对策,对同类工程设计和施工具有一定借鉴意义。更多还原

【Abstract】 The original formation balance condition are broken by the excavation of large area excavation when the large foundation pit engineering is constructed using the pile anchor technique beside the existing subway shield tunnel.The soil around the foundation pit is made under the action of unbalanced force towards the foundation pit deformation and displacement. And this unbalance effect lead to stress redistribution of the surrounding rock existing around shield tunnel. But the existing of shield tunnel is designed according to the original condition of surrounding rock, moreover the subway shield tunnel is sensitive to the rock mass deformation, it is easy to appear uneven settlement due to deformation of soil. The normal use of shield tunnel and structural safety will be threatened when the unloading influence of foundation pit excavation reaches a certain degree, such as the rail line of the requirements of train operation is’t satisfied, the shield joint bolt appear tensile fracture, the waterproofing measures of segment joint are failure, and longitudinal rupture of shield lining segments appear. So at what range the effect of excavation on nearby existing shield tunnel is strong, and construction countermeasures must be taken to ensure the normal use of shield tunnel and the successful construction of the foundation pit. Within what scope the effect of the excavation on nearby existing shield tunnel is weak even without the influence, and only need using the general auxiliary construction measures even don’t need to take countermeasures. This is a problem before the general scholars and geotechnical engineers that need to be solvedThis paper takes the project of large foundation pit near the existing the existing subway shield tunnel in Shenyang central plaza south field as the background. Longitudinal deformation curvature is determined as partition criterion on the basis of the analysis of longitudinal equivalent stiffness model. Then using large-scale finite element software Abaqus, by changing the distance between the shield and the retaining structure of foundation pit, three dimensional numerical simulation of12kinds of working conditions of the four types are established when the existing shield tunnel is located in the side of foundation pit, ground-45°direction of foundation pit, passive soil excavation area and the bottom of the foundation pit. And the surface subsidence deformation of foundation pit excavation, the deformation of existing shield tunnel and horizontal deformation of the diaphragm wall are analyzed. Main conclusions and the results are as follows:(1)Based on the research of the longitudinal equivalent stiffness model, the mechanical and mathematical relationships of the longitudinal deformation of shield tunnel radius of curvature and crack of shield tunnel segment joint and internal force of bolt is known, then the longitudinal deformation curvature radius are determined as influence judgment criterion.(2)The corresponding longitudinal deformation curvature radius of shield tunnel are respectively made as division threshold of the strong-weak affected zone and weak-without influence zone that the rail line of shield tunnel in the critical state and segment joint bolt are just in the elastic limit state. Then the construction engineering influence zoning map is established which is about the construction of foundation pit near the existing shield tunnel based on the technology of pile anchor, and some corresponding construction measures are proposed.There are some reference value design to similar engineering design and construction.更多还原