不同应力路径下大理岩的力学特性及破裂面的孕育机制

发布时间：2018-06-23 01:56

本文选题：应力路径 + 加、卸荷　；参考：《青岛理工大学》2013年硕士论文

【摘要】：随着我国人口的增长和经济建设的持续发展，人们对空间的需求已经不仅仅局限在地上部分，地下空间的开发和利用正在逐渐成为城市建设的核心。地下工程开挖是一个复杂的加、卸荷过程，，开挖过程中经常会出现坍塌、变形剧烈、岩爆等灾害，不仅影响整个工程的进度，更威胁施工人员的生命安全。因此对不同加、卸荷路径下岩体破坏机制的研究日益受到理论界和工程界的广泛重视。本文针对地下工程开挖特点，制定几种不同应力路径进行岩石加、卸荷试验研究，并在此基础上对岩石力学性质和失稳破坏机理进行探讨，从而为实际工程中判断岩体失稳提供依据。本文主要研究内容如下：（1）通过加、卸荷试验，研究不同应力路径下大理岩的力学特性。结果表明：岩石的力学性质受围压、卸荷速率及应力路径的影响，加荷及加轴压、卸围压路径下，岩样的峰值轴压、轴向应变及达到峰值点的时间均随着围压的增加逐渐增大，与围压呈线性关系。加轴压、卸围压路径下，围压相同，卸荷速率高的岩样最先发生破坏。岩样的强度、应变随卸荷速率的升高而减小，围压越高，卸荷速率对岩石变形的影响越明显。与加荷相比，卸荷能够降低岩石的承载力。加轴压、卸围压和恒轴压、卸围压两种卸荷路径中，卸荷速率较低时，加轴压卸围压路径下岩石承载力更高；卸荷速率较高时，两种卸荷路径下，岩石的变形特征没有显著差别。（2）通过岩石破坏后宏观破坏面的分析得出：岩石的破坏形态受围压和卸荷速率的影响。常规三轴试验中，主要呈现剪切破坏（单轴压缩为劈裂破坏），破坏角随围压升高而减小。加轴压、卸围压应力路径下，岩样破坏形态包括主剪切破坏、剪切加劈裂破坏和共轭剪切破坏三种。围压较低时，岩样破坏形式主要为剪切加劈裂型破坏，个别试样出现共轭破坏；围压较高时，岩样破坏以剪切为主，其中围压高且卸荷速率低时，岩样中部出现剪胀。围压相同卸荷速率愈高岩样破坏角愈大，卸荷速率相同围压愈高岩样破坏角愈小。应力控峰前恒轴压、卸围压试验中，不同卸荷速率下岩样均以剪切破坏为主，剪胀现象不明显，卸荷速率越高剪切面越小。（3）通过对破裂面的分形研究发现，用改进的立方体覆盖法进行破裂面分形维数计算时只有观测尺度小于4.2mm时，破裂面才表现出分形性质。单轴压缩路径下破裂面分形维数比常规三轴加荷大；加轴压、卸围压路径下围压较低时，破裂面的分形维数值在三种应力路径中最大，岩样破坏形态最为复杂；加轴压、卸围压路径下，大理岩破裂面分形维数值与大理岩的峰值强度、破坏强度呈相关关系。
[Abstract]:With the growth of China's population and the continuous development of economic construction, the demand for space is not confined to the upper part of the earth. The development and utilization of underground space is gradually becoming the core of urban construction. Underground engineering excavation is a complex addition and unloading process, and the collapse, severe deformation and rock burst often occur during the opening and excavation process. Such disasters not only affect the progress of the whole project, but also threaten the safety of the construction personnel. Therefore, the research on the failure mechanism of rock mass under different loading and unloading paths has been paid more and more attention by the theorists and engineering circles. On this basis, the mechanical properties of rock and the failure mechanism of instability are discussed, which provides a basis for judging the instability of rock mass in practical engineering. The main contents of this paper are as follows:
(1) the mechanical properties of marble under different stress paths are studied by adding and unloading tests. The results show that the mechanical properties of rock are affected by confining pressure, unloading rate and stress path. Under loading and loading, the peak pressure of rock samples, axial strain and the time to peak point are gradually increased with the increase of confining pressure under loading and loading and unloading confining pressure path. There is a linear relationship with the confining pressure. Under the unloading confining pressure path, the confining pressure is the same, and the rock samples with high unloading rate are the first to destroy. The strength and strain of rock samples decrease with the increase of unloading rate, the higher the confining pressure, the more obvious the effect of unloading rate on rock deformation. In the two unloading paths with constant axial pressure and unloading confining pressure, the rock carrying capacity is higher under the load unloading path with the lower unloading rate, and the rock deformation characteristics are not significantly different when the unloading rate is high, while the unloading rate is high.
(2) through the analysis of the macroscopic failure surface after rock failure, it is concluded that the failure form of rock is affected by confining pressure and unloading rate. In the conventional three axis test, the shear failure (uniaxial compression is split fracture), and the failure angle decreases with the increase of confining pressure. Under the axial compression and unloading confining pressure path, the rock specimen failure form includes the main shear failure, There are three kinds of shear fracture failure and conjugate shear failure. When the confining pressure is low, the form of rock specimen failure is mainly shear plus split type failure, and a few specimens have conjugate destruction. When the confining pressure is high, the rock sample is destroyed mainly by shear. In the case of high confining pressure and low unloading rate, the shear bulging is found in the middle of the rock sample. The higher the confining pressure is, the higher the rock sample failure is, the higher the rock sample failure. The larger the angle is, the smaller the rock specimen failure angle is, the higher the unloading rate is, the less the rock sample is under the constant pressure. In the unloading confining pressure test, the rock samples are mainly shear failure at different unloading rates, and the shear dilatancy is not obvious, the higher the unloading rate is, the smaller the shear surface is.
(3) through the fractal study of fracture surface, it is found that only when the fractal dimension of the fracture surface is less than 4.2mm when the fractal dimension of fracture surface is calculated by the improved cube covering method, the fractal dimension of the fracture surface is larger than that of the conventional three axis under the uniaxial compression path, and the fracture surface is lower when the confining pressure is lower in the unloading confining pressure path. The fractal dimension value of the three stress paths is the largest and the most complex of the rock specimen failure. Under the axial compression and unloading confining pressure path, the fractal dimension of marble fracture surface is related to the peak strength and failure strength of marble.
【学位授予单位】：青岛理工大学
【学位级别】：硕士
【学位授予年份】：2013
【分类号】：TU45

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