【作者】 周奎；

【导师】 朱维申；

【作者基本信息】 山东大学 ， 岩土工程， 2011， 硕士

【摘要】 岩体中含有丰富的节理裂隙,这些裂隙在工程开挖,水流,风的侵蚀等力的作用下起裂,扩展,相互贯通,对岩体的力学特性和破坏模式产生重要影响,同时这些裂隙相互作用产生的通道成为地下水流的重要途径,影响着岩体的渗流特性,可能腐蚀锚杆等工程材料,严重影响了岩体工程的稳定性,因此,研究多裂隙岩体的破坏机制一直是工程地质界关注的重要问题,以往的研究大多简化为平面应力或平面应变问题,但是现实中的裂隙岩体都为三维的,简化的研究方法将导致很多三维裂隙扩展的重要信息丢失,研究三维裂隙岩体的断裂机制和破坏机理将成为岩石工程界的重要方向,对岩体工程的设计,施工和稳定性具有重要作用。由于在真实岩石试件的内部很难预置有一定分布规律的多条三维裂隙。因此,研究含三维裂隙脆性岩体破坏机理的很多试验采用类岩石的相似材料来开展。因为要使模拟含三维裂隙岩体的材料力学特性,其材料尽量符合脆性岩石的主要特性,而且要在足够大的试块中要模拟有一定排列模式的多条断续节理很困难,本文采用似岩石类脆性材料开展试验,研制出脆性很高的材料,其拉压比常温下就能达到1/5,在一定低温条件下预计将可达到1/7至1/8左右。与以往的同类脆性材料相比,脆性提高了一倍。该材料透明性很好,可清晰地观察到三维内置裂隙试件的裂纹扩展的过程；在性能上与脆性岩石有较好的相似性,可以模拟多类岩石的力学特性。同时研制了可预制任意角度,条数,不同间距的三维裂隙试件模具,因此可方便制作出含二维或三维裂隙的块体试件。通过单轴压缩试验,研究了该透明脆性材料的三维裂纹产生,扩展与贯通的过程,根据应力应变曲线,泊松比系数随时间变化规律和试验时观察到的现象,可以将其过程分为初始压密,弹性变形,次生裂纹萌生和汇合,裂纹加速扩展,试件整体破坏四个阶段,试验结果表明,与二维裂纹扩展相比,三维裂纹扩展形态更加复杂,有花瓣状裂纹、包裹式翼裂纹和鱼鳍状裂纹等,完整试件抗压强度明显大于三维裂隙试件强度,变形量小于三维裂隙试件,试件破坏方式主要以劈裂破坏为主。把构成三维裂隙试件材料的单元看成是表征体元REV (representative element volume),试件破坏过程看成是表征体元的不断损伤累积的过程,利用FLAC3D中的FISH语言编制了考虑材料体元参数软化脆性破坏模型的数值计算程序,模拟了三维裂隙试件三维裂纹萌生,扩展,贯通及破坏过程。分析了在单轴压缩和双轴压缩模拟条件下不同倾角和间距试件的起裂和贯通时对应的应力,时间及损伤区的规律以及各类试件强度比较,数值模拟结果表明,脆性材料三维裂隙扩展与贯通过程比二维裂隙扩展更加复杂,其中以包裹式裂纹,花瓣状裂纹,竖直张拉裂纹扩展为主,三维裂纹各部分扩展速度不同,破坏模式为劈裂破坏。起裂应力,时间,损伤单元体积和强度随着角度和间距变化曲线呈非单调关系,贯通阶段应力,时间,损伤单元体积随着角度和间距变化曲线呈单调关系,双轴加载模拟条件下也有类似规律,这为研究含三维裂隙的脆性岩体的破坏机理具有一定的研究价值。更多还原

【Abstract】 There are abundant primary and secondary flaws in rock mass. They start the evolvement of initiation, propagation and coalescence under the influence of forces, such as engineering excavation, water flow, wind’s credibility and so on, which takes a great effect on rock strength and fracture pattern, meanwhile, the reciprocity of flaws produces many channels, which make pathway of underground water and affect rock’s seepage property, engineering materials, for example rock bolts, are likely to be eroded, all these cause bad effect on the stability of rock mass. Consequently, the failure mechanism of multi-fissured rock mass is always focused by the researchers of geology field. The engineering problems often are simplified to two-dimensional (3D) models in most of the previous studies, but fractures are 3D actually, as a result, it leads a great loss of much 3D fracture information in the simple 2D model. Researchers start to focus on the fracture mechanism and failure mechanism of 3D fractured rock mass, also theoretically significant to rock mass’s design, construction and stability.Owing to the fact that there is seldom a flaw abided by some discipline in real rock test coupons, so, analogy materials are applies in the research on failure mechanism of brittle multi-fissured rock mass. In order to simulate the properties of multi-fissured rock mass, the analogy material must satisfy the brittle rock mass’s main distinctions, furthermore, some principled flaws should be lain in a enough big rock test coupon. In the thesis, a pretty brittle analogy material is developed, whose ratio of compressive and tensile strength is 5 at normal temperature, and up to about 7 or 8 at a certain low temperature. Its brittleness is increased by one time than previous analogy materials. This analogy material is limpid enough to observe the inside 3D flaw’s evolvement of propagation; it can simulate the rock mass very well. Moulds that contain prefabricated 3D flaw of arbitrary angles, number and space are developed in succession, providing convince for the made of 2D or 3D-fractured test coupons. A high resolution vision is set before the pressing machine to record the fracture process of inside 3D flaws, and it’s more effective.From uniaxial compression, the analogy material’s evolvement of initiation, propagation and coalescence is analyzed. According to the stress-strain curve and phenomena, the process can be divided into four stages, initial compaction, elastic deformation, secondary flaws’evolvement of initiation, propagation, accelerated crack propagation, failure. From the results, it indicates that 3D crack propagation is much more complexes than the 2D crack propagation, such as, petal crack, wrapping wing crack fin crack and so on, a entire specimen has larger compressive strength and smaller deformation. The failure form mainly focuses on cleavage cracking.The full growth process of 3D flaw is simulated with volume element method with FISH programs in FLAC3D software. The uniaxial compression and multi-axial compression simulate conditions of different angles, distances, and transfixion specimens within crack, also time and corresponding stress to its evolvement of initiation and coalescence. The simulation results show that 3D crack propagation is much more complexes than the 2D crack propagation, such as the wring action of the crack plane, and the 3D coalescence pattern of cracks. The failure form mainly focuses on cleavage cracking.Corresponding stress to crack initiation, time, damaged unit size and strength is non-monotone against angle and spacing, Corresponding stress to crack coalescence, time, damaged unit size and strength is monotone against angle and spacing, and multi-axial compressive performs a similar principle. The simulation results provide a new method to further study of 3D flaw fracture.更多还原