砂性隧道围岩宏细观破坏机理及控制

发布时间：2018-11-02 09:03

【摘要】：砂性隧道围岩具有松散、破碎、低粘聚力等特性。其破坏往往具有突发性、持续性、阶段性、对扰动敏感性等特点。目前普遍采用的基于连续性假定的研究方法在砂性隧道围岩中的适用性受到限制,因此有必要从围岩细观结构出发,对其稳定性进行深入研究,在此基础上再进一步对围岩宏观结构特性和安全性进行评价。 首先,通过对砂性隧道围岩细观结构的研究,提出了围岩颗粒体系失稳破坏的细观结构模型,得到了围岩细观结构参数与宏观强度参数之间的量化关系。建立了基于细观结构失稳层面的砂性围岩破坏准则。其次,从细观颗粒接触力稳定性方面对围岩松动区产生机理和范围进行了研究,得到了隧道围岩松动区范围分析过程和方法,对各影响因素进行了详细分析。然后,在以上两阶段工作基础上,对围岩结构特性进行了深入研究,提出了复合拱结构的思想,并对其形成机理、发展演化规律、稳定性判别及其影响因素进行了分析。最后,针对砂性围岩稳定性控制原则和措施进行研究,得到砂性围岩的加固原则,并重点对注浆加固、锁脚锚杆、自适应支护结构三个方面进行论证。主要工作和结论如下： 1.砂性围岩宏观上表现出的破坏特性与其细观结构密切相关,通过对颗粒细观结构在荷载作用下的演化规律进行研究,创造性地提出了颗粒体系抗剪承载系数的概念。这一参数可以构建起细观结构参数与宏观强度参数之间的联系,在此基础上建立了两种细观结构模型—“楔块-滚动模型”和“塑性铰-楔块模型”。细观模型反映出砂性围岩的剪切破坏是应力重分布和颗粒重排列的过程,该过程中部分颗粒摩擦角不断弱化,而承载颗粒数量逐渐增多,土体内部应力分布逐渐均匀,剪切面承载力呈现先增大后减小的渐进变化过程。 2.砂性隧道围岩破坏除传统意义上的剪切破坏之外,还会发生颗粒局部失稳,在粘聚力较小的情况下,颗粒力链的局部失稳相对剪切破坏更容易发生。影响松动区范围和形态的因素主要有围岩的粘聚力、内摩擦角,侧压力系数,以及围岩所处荷载环境等因素。其中侧压力系数对松动区形态影响显著,其他参数则主要影响松动区范围,对基本形状改变不明显。 3.砂性围岩结构特性可用复合拱进行描述,复合拱的形成以及发展演化规律与围岩的三种破坏模式相对应：上部垮落-拱结构承载主体向上移动；拱脚失稳-拱跨度会向两侧移动,后续再发生高度的向上移动；下部滑移-拱结构同时在跨度和高度上向外扩展。在此过程中,设计了一种基于链式反应原理的破坏面搜索算法,可以对隧道下部滑移区进行全局搜索判断。该算法通过发散点数量、发散方位、传播距离等进行计算控制,可以有效的对潜在滑移区域进行高效搜索。 4.砂性隧道围岩的失稳破坏特征与其碎散的细观结构密切相关,在进行稳定性控制措施的制定过程中,也应针对这一特点进行相应设计。其中注浆加固、锁脚锚杆、自适应支护是比较有效的控制措施。针对性地提出了一种自适应支护结构设计构想,该结构对围岩变形具有自适应性,对施做时机不敏感,能够保证较高的前期支护刚度和稳定的后期自身受力特性。
[Abstract]:The surrounding rock of sandy tunnel has the characteristics of loose, broken, low viscosity and cohesive force. Its failure tends to have characteristics such as bursty, persistent, stage, disturbance sensitivity and so on. At present, the applicability of the research method based on continuity assumption is limited in the surrounding rock of sandy tunnel. Therefore, it is necessary to conduct deep research on the stability of surrounding rock from the meso-structure of surrounding rock, and then evaluate the macro-structure characteristics and safety of surrounding rock. First, by studying the meso-structure of surrounding rock of sandy tunnel, the meso-structure model of the failure of surrounding rock particle system is put forward, and the quantification of meso-structural parameters and macro-intensity parameters of surrounding rock is obtained. The damage of surrounding rock is established based on meso-structure instability. Secondly, the mechanism and scope of the surrounding rock loosening zone are studied from the aspect of the stability of the micro-particle contact force, and the process and method of the range analysis of the surrounding rock of the tunnel are obtained, and the influencing factors are discussed in detail. Then, on the basis of the above two stages, the characteristics of surrounding rock structure are studied deeply, the idea of compound arch structure is put forward, and its forming mechanism, evolution rule, stability discrimination and its influencing factors are analyzed. Finally, the paper studies the stability control principles and measures of sand rock surrounding rock, and obtains the reinforcement principle of sand rock surrounding rock, and puts emphasis on the three aspects of grouting reinforcement, locking foot anchor rod and self-adaptive supporting structure. Demonstration. Main work and conclusions The damage characteristics of sand-like surrounding rocks are closely related to their meso-structure, and through the study of the evolution law of the micro-structure of the particles under load, the authors creatively put forward the anti-shear bearing of the particle system. In this paper, the relation between microstructure parameters and macro-intensity parameters can be constructed. Based on these parameters, two kinds of meso-structural models, such as 鈥渨edge block-rolling model鈥，

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