主应力对围岩失稳破坏行为影响的三维数值模拟研究

发布时间：2018-05-14 05:29

本文选题：岩体力学 + 洞室稳定　；参考：《大连理工大学》2015年硕士论文

【摘要】：近几十年来,由于国家社会经济不断发展、科技水平不断提升,我国开发地下空间的工程项目越来越多,地下空间的安全稳定性也越发成为人们关心的重要内容。特别是地下工程所处的应力环境往往十分复杂,岩体通常处于三向受力状态,洞室围岩表现出了很强的非线性变形破坏特征。简单的假设为二维平面问题容易忽视轴向应力的作用及中间主应力的影响等,当涉及到破坏过程时也很难有助于深入地理解所面临的问题,有必要结合相关理论,考虑岩体的物理力学特性及破坏特征,从应力的三维效应出发研究多轴应力条件下地下洞室围岩破裂失稳的机制,为地下空间灾害监测预报、支护设计及安全稳定分析与评价等提供可靠依据。针对复杂应力环境三向应力状态下地下洞室围岩的破坏条件和破裂机制,首先采用韦伯分布建立能够描述岩体非均匀性特征的三维地质模型,以基于物理统计理论的细观损伤力学,考虑应力的三维效应,引入强度折减法,模拟洞室围岩从初始损伤到最终失稳破坏的全过程。在各种类型的三轴物理试验中,大量的前期工作都用于消除试验的端部效应,在数值模拟中通过引入强度折减法,一方面,在保持模型边界条件的同时实现洞室围岩的逐步破坏,获得围岩破裂过程和破坏模式,另一方面,可以计算得到的安全系数定量评价不同应力环境中洞室的安全稳定状况。而后,进一步探讨在不同的轴向应力和侧压力系数条件下洞室围岩的破坏模式与稳定状况,探究中间主应力对围岩破坏规律及对洞室安全稳定的影响。最后,研究了深部地下工程岩体中可能存在的分区破裂现象形成的条件及破坏的规律。论文的主要内容和成果如下：(1)研究了轴向应力分别为最小主应力、中间主应力、最大主应力时地下洞室的破坏规律以及不同轴向应力作用下洞室稳定的安全系数。结果表明,当轴向应力较小时,会促使围岩发生局部破坏,压剪破坏和拉伸破坏共同威胁着围岩的稳定；当轴向应力较大时,围岩出现间隔破裂的现象,破坏区在洞周附近分布更加均匀,洞室趋向于整体失稳模式。同时,当改变侧压力系数时,洞室轴向应力对安全系数影响的规律是不相同的。(2)研究了洞室侧压力系数取不同值时围岩破坏模式及稳定状况。结果表明,围岩岩体初始破裂形成的位置和发展的趋势受侧压力系数影响严重。当侧压力系数较小时,破裂首先产生在洞室两壁附近,而后局部破裂带不断向围岩深处发展,威胁洞室的安全稳定；当侧压力系数较大,偏压水平不高时,破坏区在洞室周围分布更加均匀,但是破裂形式复杂,总体上呈现出了整体破坏的模式。同时随着围岩侧压力系数的增加,洞室安全稳定性基本上表现出逐步提高的趋势,但安全系数提高的快慢因轴向应力的不同而存在着明显差异。(3)探究了不同中间主应力作用下洞室围岩的破坏规律和安全稳定状况。结果表明,中间主应力对洞室围岩破坏规律有着显著的影响,同时,地下洞室围岩的安全稳定性具有中间主应力效应,不同方向的中间主应力影响地下洞室安全状况的规律是不同的。当轴向应力作第二主应力时,安全系数总体呈现出了大小不同的两个阶段；当水平应力作第二主应力时,安全系数随其增加而先增加后减小。(4)探讨了地下洞室埋深较大时围岩分区破裂形成的条件和力学机制。当洞室轴线方向与最大水平应力方向平行时,较大的轴向应力会引起洞室径向较大的张拉作用,促使洞室围岩产生分区破裂化现象。同时,分区破裂化的形成需要满足适当的条件,岩体可能并没有形成完整且典型的分区破裂现象,而是出现了具有分区破裂化趋势的局部破坏。
[Abstract]:In recent decades, because of the continuous development of the national social economy and the continuous improvement of the level of science and technology, there are more and more projects in the development of underground space in China, and the safety and stability of underground space is becoming more and more important. Especially, the stress environment of underground engineering is often very complex, and the rock mass is usually in the form of three direction force. The surrounding rock of the cavern shows a strong nonlinear deformation and failure characteristics. The simple assumption that the two-dimensional plane problem is easy to ignore the effect of the axial stress and the influence of the intermediate principal stress, and so on. When it is involved in the failure process, it is difficult to understand the problems in depth. It is necessary to combine the relevant theories and consider the physical mechanics of the rock mass. From the three-dimensional effect of stress, the mechanism of fracture and instability of surrounding rock in underground caverns under multi axis stress conditions is studied. It provides reliable basis for underground space disaster monitoring and prediction, support design, safety and stability analysis and evaluation, and the failure conditions of underground cavern surrounding rock under the three direction stress state of complex stress environment. The fracture mechanism, firstly, uses Webb distribution to establish a three-dimensional geological model that can describe the heterogeneity of rock mass. Based on the meso damage mechanics based on the theory of physical statistics, the three-dimensional effect of stress is considered, and the strength reduction method is introduced to simulate the whole process of the surrounding rock from initial damage to final instability failure. In various types of three axis physics In the experiment, a large amount of early work is used to eliminate the end effect of the test. In the numerical simulation, the strength reduction method is introduced. On the one hand, the progressive destruction of the surrounding rock is realized while the boundary condition of the model is kept. The fracture process and failure mode of the surrounding rock are obtained, and the other side, the calculation of the quantitative evaluation of the safety coefficient is different. The safety and stability of the caverns in the stress environment. Then, the failure modes and stability conditions of the surrounding rock of the caverns under the conditions of different axial stress and side pressure coefficient are further explored, and the influence of the middle principal stress on the failure law of the surrounding rock and the safety and stability of the caverns is explored. Finally, the possible subareas in the rock mass of the deep underground engineering are studied. The main contents and results of the paper are as follows: (1) the failure laws of the underground caverns and the stability of the caverns under the action of different axial stresses are studied. The results show that the axial stress is less than that of the axial stress. In order to cause local destruction of the surrounding rock, the pressure shear failure and tensile failure threaten the stability of the surrounding rock. When the axial stress is larger, the surrounding rock occurs interval rupture, the distribution of the damaged area is more uniform around the hole and the cavity tends to the overall instability mode. At the same time, when the side pressure coefficient is changed, the axial stress of the cavern is influenced by the safety factor. The law of the noise is different. (2) the failure mode and stability of the surrounding rock are studied. The results show that the position and development trend of the initial fracture of rock mass is seriously affected by the side pressure coefficient. When the side pressure coefficient is small, the fracture first occurs near the two wall of the cave, then the local rupture is then broken. With the continuous development of the surrounding rock, it threatens the safety and stability of the caverns. When the lateral pressure coefficient is large and the horizontal pressure is not high, the distribution of the damaged area is more uniform around the cavern, but the fracture form is complex and the overall failure mode is presented. At the same time, with the increase of the lateral pressure coefficient of the surrounding rock, the safety and stability of the cavern is basically shown. There is a trend of gradual improvement, but the increase of safety factor has obvious differences due to the difference of axial stress. (3) the failure law and safety and stability condition of the surrounding rock in the caverns under different intermediate principal stresses are explored. The results show that the intermediate principal stress has a significant influence on the failure rules of the surrounding rock, and the surrounding rock of the underground cavern. The safety stability has the intermediate principal stress effect, and the law of the underground cavern safety condition is different in different directions. When the axial stress is second main stresses, the safety factor generally presents two stages of different sizes; when the horizontal stress is second main stresses, the safety coefficient increases with it and increases first. (4) the conditions and mechanical mechanism of the subarea fracture of the surrounding rock are discussed. When the axis direction of the cavern is parallel to the maximum horizontal stress direction, the larger axial stress will cause the larger radial tensile action of the cavern, which will cause the fragmentation of the surrounding rock mass. At the same time, the formation of subarea fracture is formed. It is necessary to meet the appropriate conditions. The rock mass may not have formed a complete and typical zonal rupture phenomenon, but a partial failure with the trend of zonal fracturing.

【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U451.2;TU91

【共引文献】