【作者】 郭彦双；

【导师】 朱维申； Robina H.C. Wong；

【作者基本信息】 山东大学 ， 工程力学， 2007， 博士

【摘要】 岩体中原生裂隙的起裂、扩展和贯通演化特性、破裂模式及其对工程岩体强度及渗流特性的影响一直为工程地质界、岩石力学界和相关工程界所重视。由于三维裂隙岩体问题的复杂性，以往的研究大多将三维问题简化为二维问题来研究，并取得了较为系统的研究成果。但是裂隙岩体的二维简化模型往往会丢失许多裂纹扩展与贯通过程的三维信息。因此，近年来三维裂隙岩体的断裂损伤机理及其力学特性的研究逐渐成为裂隙岩体工程领域的重要课题之一，对于裂隙岩体工程的设计、施工和长期稳定性的维护具有极其重要的指导作用，对于地震地质学科和地球物理研究领域也具有一定理论意义。针对三维裂隙岩体试验模型材料的选取问题，在总结以往试验材料的基础上，研制出两种不同的脆性材料，一种是透明性良好的低温脆性聚酯树脂材料，其拉压比可达1／5，优于以往的其他模拟材料，该材料属于均质材料，并可清晰地观察到试样内裂纹扩展的三维状态；另一种是类岩石材料，其脆性程度非常好，拉压比可达1／23。分析了岩体在断裂过程中的裂隙效应和裂隙的维数效应及裂隙萌生的基本力学模式，给出了单轴压缩条件下几种新生裂纹的定义，如：翼裂纹、反翼裂纹、包裹式翼裂纹和贝壳状裂纹等。采用室内宏、细观力学试验研究了不同脆性材料中三维裂纹萌生、扩展及其贯通的演化过程。采用透明树脂材料的试验结果表明：三维裂隙起裂、扩展是以包裹式翼裂纹为主要扩展模式的；并在实验中获得了一些以往研究中所未观察到的裂纹扩展模式，如穿越裂纹、花瓣状裂纹等。对于不透明的真实岩石及类岩石材料，在单轴压缩状态下，试样破裂后可以清楚地观察到包裹式翼裂纹的扩展，但无法在这类材料中区分到其他形式的裂纹。此外，材料的均匀性将影响含三维裂隙的最终断裂形态。含三维裂隙的均匀树脂试样最终是以劈裂破坏为主的，但在类岩石材料试样却是以剪切断裂的。这样，可根据岩体表面上的断裂迹线与预制裂隙方位之间的关系推定岩体内三维裂隙的赋存状态，为确定裂隙岩体的锚固方式提供参考。采用三维声发射定位技术研究了类岩石材料中内置裂隙单轴压缩条件下的断裂模式及其声发射特征，提出三维裂隙起裂强度的判定方法，并可判定三维裂纹稳定扩展与失稳扩展状态，为工程检测岩体裂隙破裂的演化状态提供一种新解决方案。此外，还讨论了一定条件下三维裂隙间距和密度对岩体强度的影响。在单轴压缩荷载作用下，裂隙深度比d／t(d，为裂隙深度；t为试样的厚度)直接影响三维裂纹的扩展过程和断裂模式。实验结果表明：在单轴压缩荷载作用下，当裂隙深度比d／t＜0.6时，岩石中表面裂隙(非穿透裂隙)的扩展模式与穿透裂隙扩展模式有着本质的不同，反翼裂纹模式成为试样破裂的主导方式，且反翼裂纹的起裂位置并不在预制裂隙尖端处，而是预制裂隙端部附近的某一区域；次生的翼裂纹只在试验后期出现。当d／t＞0.6时，表面裂隙以主要翼裂纹模式断裂。在砂岩试样亦观察到相似的现象。声发射定位结果亦支持了这一全新的试验现象，并且表明裂纹的起裂是从试样的内部开始的。此外，对于表面裂隙，表面裂隙倾角α对岩样的起裂应力影响很显著。根据经典的脆性断裂力学理论和弹性理论，研究了三维裂隙扩展的最大拉应力准则，推导出单轴压缩条件下考虑Ⅰ-Ⅱ-Ⅲ完全复合型三维裂隙前缘逐点的应力状态的计算公式，讨论了裂隙边界上各点的最大拉应力、破裂面弯角和扭角的变化情况，用数值方法确定了破裂面的起裂位置及起裂方向。理论分析结果与实验结果取得了很好的一致性。脆性材料的断裂过程可看成是构成材料的表征体元RVE(representative volume element)损伤累积的过程。在数值计算中，基于快速拉格朗日方法，利用FLAC3D中的FISH语言编制了考虑材料体元参数软化模型的数值计算程序，模拟了三维裂隙扩展贯通过程。数值模拟结果表明，以往将裂隙扩展简化为二维问题进行分析研究，会失去许多三维裂隙扩展的重要信息，如三维裂纹扩展面的扭转，三维裂纹贯通模式等。借助于三维裂纹的数值模拟可以清楚地了解三维裂纹扩展及贯通的全貌，以弥补三维裂隙断裂试验与理论研究的不足，为进一步研究三维裂隙断裂的本质提供一定的参考价值。更多还原

【Abstract】 Some problems, such as the evolvement and fracture pattern of initiation, propagation and coalescence from some primary flaw in rock mass, and the influence on rock strength and seepage property, are always focused by the researchers of geology field, rock mechanics and other corresponding fields. Owing to the complexion of three-dimensional (3D) fractured rock mass, the engineering problems often is simplified to two-dimensional (3D) models in most of the previous studies. But, much 3D fracture information is fully reflected in the simple 2D model. So, recently, some researchers start to focus on the fracture mechanisms and properties of 3D fractured rock mass. These jobs are very important, directive and practical to the design, construction and stability of fractured rock mass, also theoretically significant to earthquake geology science and earth physics fields.Make two brittle materials based on some previous studies. One is a transparent frozen resin, a new type mean material, it’s ratio of compressive and tensile strength is about 5; another is a new rock-like material, its components are cement and good sand, the ratio of compressive and tensile strength is up to 23.The flaw effect, dimension effect and basic facture pattern during rock failure is analyzed, first. Several new crack patterns are defined, such as wing crack, anti-wing crack, wrapping wing crack and shell-shaped crack. Then, a series of experiments on the growth and coalescence of 3D flaw in different brittle materials are carried out. The experiments in mean material show that: the wrapping crack is an important pattern for the growth and coalescence 3D flaw; some new growth cracks are observed in the experiments, such as cross crack and petal crack. The cross crack is induced from tensile and tearing stress along the boundary of the flaw plane, it belongs to a mixed mode fracture of Mode I and Moded III. The petal crack is induced from the pure tearing stress, is a fracture of Mode III. The commence of the two types of cracks makes the stress states more complicated near the flaw boundary, and mostly can not be expressed with math equations. For the non-transparent materials, the wrapping wing crack also is observed after splitting the samples. This type of crack belongs to a fully mixed fracture of Mode I, Mode II and Mode III. But, other types of cracks are not observed, directly. Although the internal cracks patterns can not be seen, the flaw configuration in rock mass may be deduced according to the output crack lines on the surface of samples (rock mass), and provide a conference information for the engineering bolted design.For the further study of the fracture of 3D flaw, the acoustic emission (AE) located technique is studied the growth pattern of 3D flaw and AE properties under uniaxial compression, and provide a method to confirm the different stages (initiation, propagation and coalescence) according to the AE properties during the flaw fracture. Then, the strength influence from the spacing and density of 3D flaw are analyzed. For the fractures of surface flaw, the depth ratio d/t (d, flaw depth; t, sample thickness) of the flaw plays an important role on the pattern and growth process of the 3D surface flaw. As d/t<0.6, the facture pattern of 3D surface flaw is very different from 2D through flaw, anti-wing crack is main fracture pattern of surface flaw, wing crack is primary for d/t>0.6. And the same phenomena also are recorded in sandstone and gabbro samples. The results from AE location further supports the new fracture pattern and shows that the anti-wing crack starts to grow within the sample. Furthermorem, the inclined angle of the flaw will main influence the initiation stress of crack.Based on the classical rock fracture theory and elastic theory, the maximum tensile stress flaw is revised. The stress state of any point along the flaw boundary is deduced during uniaxial compression, according to the full mixed fracture mode (Mode I-II-III). The results from the theoretical analysis shows that: the main initiation fracture emerges within a zone near the end tips of the long axis of the flaw, not limited to the tips, the crack almost synchronously initiated in the zone. The bend angle of main crack is very big, the wring angle is small, but not equal to zero. The secondary cracks also synchronously initiated in the middle of the flaw boundary line. At the end tips of the short axis of the flaw, the secondary crack planes only have a bend angles, the wring angle is equal to zero. The results from the above revised maximum tensile stress flaw are the same as that of experiments.The full growth process of 3D flaw is simulated with volume element method with FISH programs in FLAC3D software. The simulation results show that: 2D mode will lose much 3D growth information of cracks, such as the wring action of the crack plane, and the 3D coalescence pattern of cracks. The simulation results provide a new method to further study 3D flaw fracture, and make up some faults of the experimental results.更多还原