地下工程中若干失稳破坏问题的机理和冗余度研究

发布时间：2018-01-17 13:16

本文关键词：地下工程中若干失稳破坏问题的机理和冗余度研究　出处：《天津大学》2014年博士论文　论文类型：学位论文

【摘要】：在城市化进程中，地下空间的利用成为趋势。然而由于地下工程固有的复杂性，使得地下工程事故，例如深基坑的垮塌和隧道开挖面的失稳等，时有发生。然而目前对于这些失稳破坏问题的产生发展机理、仿真模拟方法及预防控制理论等研究较少，没有形成系统的理论体系，限制了地下工程的建设与发展。本文将大变形计算方法离散元（DEM）和物质点法（MPM）应用于若干地下工程失稳破坏问题的模拟和机理研究中，同时针对地下工程连续破坏的控制提出冗余度设计理论，主要内容如下。（1）对深基坑工程连续倒塌和冗余度研究的必要性进行了分析，指出基坑工程中冗余度研究的目的、分类和作用，并且对两个典型事故中的冗余度问题进行了剖析，初步总结了基坑工程中的冗余度设计方法。（2）利用离散元对基坑环梁支撑结构的连续破坏进行了模拟，并且提出了一种适用于基坑支撑体系的冗余度评价指标，进而对不同环梁支撑方案的冗余度进行了定量对比，结果表明，利用合理增加传力路径等措施可以有效提高支撑体系冗余度。（3）以探究支撑端部连接对支护结构冗余度的影响为出发点，对两种连接情况的基坑的破坏过程进行了离散元模拟，对其中的连续破坏现象进行了分析。结果表明支护体系冗余度的提高可以有效抵抗连续破坏的发生，防止基坑在局部破坏情况下导致整体崩溃。（4）利用有限元和MPM从小变形及大变形两方面对两级支护基坑进行了剪切滑动面开展及变形破坏等方面的分析。总结了无支撑多级支护基坑的变形、稳定、剪切面发展及协同工作机理等特点，为进一步深入系统分析这种新型支护方法打下了理论与方法上的基础。（5）传统的隧道开挖面稳定计算方法仅能得出稳定安全系数，并不能提供开挖面的破坏过程、破坏形态及破坏程度等信息。因此将MPM应用于隧道开挖面的失稳破坏模拟中，首先利用已有的离心机试验结果和解析方法对MPM计算进行了验证，进而系统研究了土质条件、土体强度分布、埋深、无支护段长度等因素对开挖面破坏机理和程度的影响，为隧道设计和风险评估提供了参考。
[Abstract]:In the process of urbanization, the utilization of underground space has become a trend. However, due to the inherent complexity of underground engineering, underground engineering accidents, such as the collapse of deep foundation pit and the instability of tunnel excavation surface, etc. However, at present, there are few researches on the mechanism, simulation and control theory of these instability and failure problems, and no systematic theoretical system has been formed. It limits the construction and development of underground engineering. In this paper, the discrete element method (DEM) and the material point method (MPM) are applied to the simulation and mechanism study of instability and failure of some underground engineering. At the same time, the redundancy design theory is put forward for the continuous failure control of underground engineering, the main contents are as follows. 1) the necessity of continuous collapse and redundancy study of deep foundation pit engineering is analyzed, and the purpose, classification and function of redundancy research in foundation pit engineering are pointed out. The redundancy problem in two typical accidents is analyzed, and the design method of redundancy in foundation pit engineering is preliminarily summarized. 2) the continuous failure of bracing structure of ring beam of foundation pit is simulated by discrete element, and a redundancy evaluation index suitable for bracing system of foundation pit is put forward. Furthermore, the redundancy of different bracing schemes is compared quantitatively. The results show that the redundant degree of bracing system can be effectively improved by using reasonable increase of load transfer path and so on. In order to explore the influence of support end connection on the redundancy of supporting structure, the failure process of foundation pit with two kinds of connections is simulated by discrete element method. The results show that the increase of redundancy of supporting system can effectively resist the occurrence of continuous failure and prevent the foundation pit from collapsing under the condition of local failure. In this paper, finite element method and MPM are used to analyze the shear sliding surface and deformation failure of two-stage supporting foundation pit, and the deformation of multi-stage braced foundation pit is summarized. The characteristics of stability, shear plane development and cooperative working mechanism lay a theoretical and methodological foundation for further and systematic analysis of this new support method. 5) the traditional calculation method of tunnel excavation surface stability can only obtain the stability safety factor, and can not provide the damage process of the excavated surface. Therefore, MPM is used to simulate the instability of tunnel excavation surface. Firstly, the existing centrifuge test results and analytical methods are used to verify the calculation of MPM. Furthermore, the influence of soil condition, soil strength distribution, buried depth, length of unsupported section on the failure mechanism and degree of excavation surface is studied systematically, which provides a reference for tunnel design and risk assessment.
【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU91;TU753

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