双开关西原模型及其在地下洞室三维流变分析中的应用

发布时间：2018-03-19 16:28

  本文选题：软岩　切入点：地下洞室　出处：《武汉大学》2017年硕士论文　论文类型：学位论文

【摘要】：随着我国经济的快速发展和城市化的推进,水利、能源、交通、国防等基础设施建设更多地涉及地下空间开发,地下工程施工面临更多新挑战、新问题,软岩地下洞室长期稳定往往是工程能否顺利完成的关键。本文以云南省滇中引水工程凤屯隧洞为依托,从软岩流变物理特性出发,提出新的理论模型,开发地下洞室三维流变数值仿真计算程序,针对软岩地下洞室施工开挖过程中的流变机理、围岩变形特性和支护结构受力状态展开进一步的数值研究,旨在为今后工程设计施工提供合理建议,确保工程的可行性、安全性和经济性。主要内容如下:(1)归纳软岩流变特性、数值计算方法和地下洞室存在的流变问题,研究经典的岩石流变理论西原模型的含义。结果表明:西原模型存在两个问题:其一,不能准确地描述软岩单轴压缩状态下的典型蠕变发展过程,特别是应变率随时间增大的加速蠕变阶段;其二,只考虑应力和长期强度的关系,复杂应力状态下未考虑屈服函数对应力状态的评判作用,进而影响施加黏塑性应变时间点的判断。(2)针对西原模型存在的两个问题,在西原模型的基础上,引入塑性屈服函数以及应力水平和长期强度的大小关系两个开关函数,建立包含流变时间、应力水平和塑性屈服函数等在内的双开关西原模型。结果表明:双开关西原模型能够反映不同岩石或者同种岩石在不同的应力水平下的蠕变过程;进行复杂应力状态条件下的三维本构推演,为后续三维流变有限元程序开发奠定理论基础。(3)引用增量变塑性刚度初应变法,根据双开关西原模型理论进行三维推演,结合软岩地下洞室施工开挖流程和支护原则,开发地下洞室三维流变有限元程序。结果表明:增量变塑性刚度初应变法能够取得较快的计算速度和较稳定的收敛效果;编制的计算程序实现了洞室开挖静力、支护和流变效应数值模拟的统一,为评判软岩地下洞室围岩稳定性和支护安全性提供计算平台。(4)基于邱贤德等完成的软岩单轴压缩物理试验,利用编制的地下洞室三维流变有限元程序进行软岩单轴压缩数值试验,开展基于双开关西原模型的毛洞流变效应研究。结果表明:物理试验和数值试验曲线拟合优度较高,毛洞流变过程中围岩损伤区和位移值不断增大将发生破坏,该理论能够更为准确地模拟物理试验反映的软岩流变过程,合理地模拟出软岩洞室毛洞开挖完成后的流变特点。(5)针对滇中引水工程凤屯隧洞的地质特点,选择典型的Ⅳ类软岩洞段进行洞室开挖、支护和160天流变效应研究。结果表明:毛洞开挖、一次支护条件下,临空面围岩变形大、受压损伤严重、局部锚杆失效;必须施加二次支护,拟定衬砌结构能够长期抵抗围岩挤压作用,有效地限制软岩变形和塑性损伤区发展,改善洞周围岩应力状态,确保锚杆长期发挥支护作用,实现隧洞的长期稳定。
[Abstract]:With the rapid development of China's economy and the promotion of urbanization, the construction of water conservancy, energy, transportation, national defense and other infrastructure facilities are more involved in the development of underground space, and the construction of underground engineering is facing more new challenges and new problems. The long-term stability of soft rock underground caverns is often the key to the successful completion of the project. Based on the Fengtun Tunnel, a water diversion project in central Yunnan Province, a new theoretical model is proposed based on the rheological and physical characteristics of soft rock. A numerical simulation program for 3D rheology of underground caverns is developed to further study the rheological mechanism, deformation characteristics of surrounding rock and mechanical state of supporting structures during excavation of underground caverns in soft rock. In order to provide reasonable suggestions for future engineering design and construction, to ensure the feasibility, safety and economy of the project, the main contents are as follows: 1) Induction of rheological characteristics of soft rock, numerical calculation method and rheological problems existing in underground cavern, The meaning of the classical rock rheological model is studied. The results show that the model has two problems: first, it can not accurately describe the typical creep development process of soft rock under uniaxial compression. In particular, the accelerated creep stage in which the strain rate increases with time; secondly, the relationship between stress and long-term strength is considered only, and the effect of yield function on the stress state is not considered in complex stress state. Then influence the judgment of time point of viscoplastic strain. (2) aiming at the two problems existing in Xiyuan model, the plastic yield function and the relationship between stress level and long-term strength are introduced on the basis of Xiyuan model, and two switching functions are introduced. The double Kansai original model, including rheological time, stress level and plastic yield function, is established. The results show that the double Kansai original model can reflect the creep process of different rocks or the same rock at different stress levels. The three-dimensional constitutive model under complex stress state is derived, which lays a theoretical foundation for the subsequent development of three-dimensional rheological finite element program. The incremental variable plastic stiffness initial strain method is used to derive the three-dimensional constitutive equation according to the original model theory of Shuangkaikansai. Combined with the excavation process and supporting principle of soft rock underground cavern, the three-dimensional rheological finite element program is developed. The results show that the incremental variable plastic stiffness initial strain method can obtain faster calculation speed and more stable convergence effect. The calculation program has realized the unification of static force, support and rheological effect numerical simulation of cavern excavation. In order to evaluate the surrounding rock stability and support safety of soft rock underground caverns, this paper provides a calculation platform. 4. Based on Qiu Xiande et al., the physical test of soft rock uniaxial compression is carried out. The three-dimensional rheological finite element program of underground cavern is used to carry out uniaxial compression numerical test of soft rock, and the rheological effect of Mao cave is studied based on the original model of double kaikansi. The results show that the fitting degree of physical test and numerical test curve is high. The damage zone and displacement value of surrounding rock will be destroyed during the rheological process of cavern, and the theory can more accurately simulate the rheological process of soft rock reflected by physical test. According to the geological characteristics of Fengtun tunnel in central Yunnan water diversion project, the typical type 鈪，

本文编号：1635071