圆形装配式基坑支护结构受力及施工过程数值分析

发布时间：2018-03-23 01:25

本文选题：装配结构　切入点：基坑　出处：《中国地质大学(北京)》2017年硕士论文　论文类型：学位论文

【摘要】：装配式基坑支护结构能够实现方便施工、缩短工期、节约成本的目的,在盾构、顶管等地下工程施工中的竖井支护工程中得到了广泛应用。盾构、顶管工程中的竖井数量多、工期紧、规格单一、环境复杂、安全要求高,且属于临时性工程,在工程完成后需要进行支护结构拆除和基坑回填处理,这正是装配式支护结构的优点。前期研究成果主要集中在单一构件或单层拼装结构的强度和受力特性,但是对于通过环向和竖向连接构件组合而成的圆筒形结构体系的整体受力性能尚缺乏研究。此外,装配式结构施工中其支护深度滞后于开挖深度一定距离(单次开挖深度),越向下开挖,单次开挖后尚未支护前的临空面的稳定性越差,需要明确给定单次开挖深度下基坑能保持稳定的最大开挖深度。采用SAP2000结构有限元程序建立由标准钢板构件、环向预紧构件和竖向连接构件组成的三维结构有限元模型,根据装配式支护体系的结构特点,按JGJ130-2011《建筑施工扣件式钢管脚手架安全技术规范》对装配式支护结构在永久荷载和施工荷载的多种组合工况下的受力和变形进行分析。结果表明,在不利荷载组合工况下的装配式支护结构承载力具有足够安全储备,能够满足规范要求。基于PLAXIS2D岩土有限元程序构建了考虑土-结构-地下水相互作用的基坑数值模型,模拟装配式结构支护基坑分层开挖、分层支护的施工过程,重点分析了不同单次开挖深度对基坑最大开挖深度的影响,得到以下结论:在砂性土和软土层中,随着基坑的单次开挖深度的增加,基坑最大开挖深度依次减小。在粘性土层中,由于粘性土的粘聚力、内摩擦角以及土体刚度参数对基坑的最大开挖深度的影响较大,基坑的单次开挖深度对基坑的对大开挖深度影响并不明显。但在软土层中,由于单次开挖深度越大,暴露出的临空面越多,而软土的刚度较小,易发生变形,因此临空面处的土体容易达到破坏状态,进而导致软土层中基坑的最大开挖深度的值相对较小。
[Abstract]:The prefabricated foundation pit supporting structure can realize the purpose of convenient construction, shorten the construction period and save the cost. It has been widely used in the shaft support engineering in the underground engineering such as shield, pipe jacking and so on. There are many vertical wells in shield and pipe jacking engineering. The construction period is tight, the specification is single, the environment is complex, the safety requirement is high, and belongs to the temporary project. After the completion of the project, it is necessary to carry out the demolition of the supporting structure and the treatment of the foundation pit backfill. This is the advantage of the assembled support structure. The previous research results mainly focus on the strength and mechanical characteristics of the single component or monolayer assembly structure. However, there is a lack of research on the overall mechanical behavior of the cylindrical structural system formed by the combination of annular and vertical connection members. In the construction of prefabricated structure, the support depth lags behind the excavation depth (the lower the excavation depth is, the worse the stability of the goaf surface before the excavation is not supported, the lower the excavation depth is, the lower the excavation depth is. It is necessary to make sure that the maximum excavation depth of the foundation pit can be kept stable under the order excavation depth. A three-dimensional structural finite element model consisting of standard steel plate member, circumferential preload member and vertical connection member is established by using SAP2000 structural finite element program. According to the structural characteristics of assembly support system, According to JGJ130-2011, the stress and deformation of assembled support structure under various combined conditions of permanent load and construction load are analyzed. The results show that, The bearing capacity of prefabricated support structure under unfavorable load combination condition has enough safety reserve and can meet the requirements of code. Based on PLAXIS2D geotechnical finite element program, a numerical model of foundation pit considering soil-structure-groundwater interaction is established. This paper simulates the construction process of layered excavation and layered support of prefabricated structure supporting foundation pit. The influence of different single excavation depth on the maximum excavation depth of foundation pit is analyzed, and the following conclusions are obtained: in sandy soil and soft soil, With the increase of single excavation depth of foundation pit, the maximum excavation depth of foundation pit decreases in turn. In the clay soil, the cohesive force, the angle of internal friction and the stiffness parameter of soil have great influence on the maximum excavation depth of foundation pit. The single excavation depth of foundation pit has no obvious effect on the large excavation depth, but in the soft soil, the larger the excavation depth, the more the exposed goaf surface, and the smaller the stiffness of the soft soil is, the more deformation occurs. Therefore, the failure state of soil is easy to reach, which leads to the relatively small value of the maximum excavation depth of foundation pit in soft soil.
【学位授予单位】：中国地质大学(北京)
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU753

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