临近地铁隧道的基坑支护变形控制

发布时间：2018-01-25 04:30

本文关键词： 基坑支护变形弹性抗力地下连续墙　出处：《吉林大学》2013年硕士论文　论文类型：学位论文

【摘要】：随着我国城市轨道交通建设的快速发展，临近地铁隧道的基坑工程越来越多。这类在地铁隧道附近开挖的基坑工程对地铁隧道的影响表现在三个方面。第一，由于开挖的卸载，引起隧道结构的位移；第二，，围护结构在施工期间，尚未发挥作用时也会引起隧道结构的位移；第三，庞大体量的建筑荷载在加载后会再次引起隧道结构的位移。上述三个方面严重地影响着地铁的运营安全。因此，在基坑支护结构设计时，起决定性因素的是支护结构的变形控制。由于基坑开挖引起的变形影响因素众多，迄今为止尚难得出较为准确的定量结论，基坑支护墙后土体的位移场在一般的分析软件中均未涉及，大型三维数值分析软件的建模又比较复杂，难以在所有工程中应用。因此，如何在一般的工程项目中耦合支护结构的变形与周边土体的位移场十分重要。本文结合北京外交公寓基坑工程，从基坑支护结构的设计计算原理出发，基于同济启明星深基坑支护分析软件FRWS7，按照平面应变问题采用弹性抗力有限单元法进行支护结构的设计，再根据支护结构的位移，利用土体位移场的简单解析法求解基坑周边任意点的位移。以临近基坑的隧道底部控制位移作为设计输入条件进行基坑支护结构的设计，同时运用基于FLAC3D的数值分析方法进行应力应变分析。运用上述两种分析方法对本基坑工程进行了分析，继而得出根据变形控制为原则的基坑支护设计方案—采用复合土钉墙+地下连续墙的方案进行基坑支护。监测数据表明弹性抗力有限元法计算得到的支护结构变形与实际监测数据相当，按照基坑周围土体位移场的简单解析法计算得到的隧道结构位移与实际监测的数据相吻合，说明了简单解析法基本适用于北京地区的土体位移场计算。基于FLAC3D的连续介质数值分析方法在模拟基坑工程等岩土体材料方面的位移场与实际监测数据符合性较好，对于复杂环境条件下的基坑分析设计有独特的优势。地下连续墙在施工中成槽是关键，该工程对地下连续墙与隧道间分布的易于坍塌的粉土及砂类土进行了水泥土搅拌桩的加固，减小了地下连续墙对隧道的影响。土方开挖充分考虑边坡的时空效应，分时分段采取抽条式开挖，有效地控制了基坑变形。通过分析监测数据的平面分布特征可以发现，支护结构的变形和内力最大值均出现在基坑剖面中部，是边坡空间效应的具体表现，基坑阴角处的位移及内力均较小，角隅作用明显。
[Abstract]:With the rapid development of urban rail transit construction in China, there are more and more foundation pit projects near the subway tunnel. The displacement of tunnel structure is caused by the unloading of excavation. Second, the surrounding structure will also cause the displacement of the tunnel structure when it has not played a role during the construction period; Third, the large volume of building load will cause the displacement of tunnel structure again after loading. The above three aspects seriously affect the safety of subway operation. Therefore, in the foundation pit support structure design. The decisive factor is the deformation control of the supporting structure. Because there are many factors affecting the deformation caused by the excavation of foundation pit, it is difficult to get a more accurate quantitative conclusion so far. The displacement field of soil behind the retaining wall of foundation pit is not involved in the general analysis software, and the modeling of large-scale three-dimensional numerical analysis software is complex, so it is difficult to be applied in all projects. It is very important to analyze the deformation of coupling support structure and the displacement field of surrounding soil in general engineering projects. In this paper, based on the design and calculation principle of foundation pit support structure, based on Tongji Qi-star deep foundation pit support analysis software FRWS7, combined with Beijing diplomatic apartment foundation pit project. According to the plane strain problem, the elastic resistance finite element method is used to design the supporting structure, and then according to the displacement of the supporting structure. The displacement of any point around the foundation pit is solved by the simple analytical method of the displacement field of soil, and the control displacement of the tunnel bottom near the foundation pit is taken as the design input condition to design the supporting structure of the foundation pit. At the same time, the stress and strain analysis is carried out by using the numerical analysis method based on FLAC3D, and the foundation pit engineering is analyzed by the above two analysis methods. Then, according to the principle of deformation control, the design scheme of foundation pit support is obtained, which is based on composite soil nailing wall. The monitoring data show that the deformation of the supporting structure calculated by the finite element method of elastic resistance is equivalent to the actual monitoring data. The displacement of tunnel structure calculated by simple analytical method according to the displacement field of soil around foundation pit coincides with the actual monitoring data. It is shown that the simple analytical method is suitable for the calculation of soil displacement field in Beijing area. The displacement field and actual monitoring number of continuous medium numerical analysis method based on FLAC3D in simulating rock and soil materials such as foundation pit engineering are discussed. According to good conformity. It has a unique advantage for foundation pit analysis and design under complex environment. Grooving is the key in the construction of underground continuous wall. The cement soil mixing pile is used to reinforce the silt and sand soil which is easy to collapse between underground continuous wall and tunnel. The influence of underground continuous wall on tunnel is reduced. The time and space effect of slope is fully considered in earthwork excavation. By analyzing the plane distribution characteristics of the monitoring data, it can be found that the maximum deformation and internal force of the supporting structure appear in the middle of the foundation pit section, which is the concrete manifestation of the slope spatial effect. The displacement and internal force at the bottom corner of foundation pit are smaller, and the corner effect is obvious.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU753

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