基于声发射和图像处理技术对类岩石材料破裂过程的模型试验研究

发布时间：2018-06-17 16:12

本文选题：裂纹试样 + 破坏模式　；参考：《重庆大学》2015年硕士论文

【摘要】：由于复杂的地质构造和赋存条件,岩石是一种典型的不连续介质,存在一些如矿物解理、微裂隙、粒间空隙、晶格缺陷等内部缺陷。国内外学者经过大量研究发现,在受力的情况下,这些软弱结构面会张开、扩展并贯通引起岩石的失稳甚至破坏。因此,进行含预制裂纹试样的相似模型试验研究,对实际工程有重要的指导意义。关于含两根预制裂纹的试样,学者们做了大量的研究工作,但没有综合考虑空间布置对试样破坏过程的影响。本文为了研究裂纹空间布置因素对起裂模式、破坏模式、试样力学特性以及试样表面位移变化的影响,基于声发射和图像处理技术主要做了以下工作并取得了相应成果:①对预制裂纹尖端微裂纹出现的先后顺序进行了描述,并对新生裂纹的类型进行了归类:翼型裂纹,次生共面裂纹和次生倾斜裂纹。考虑了裂纹的空间布置因素对起裂模式和破坏模式影响:随着裂纹倾角增大,当裂纹间距比较小时,试样破坏模式由剪切破坏向张拉破坏转变,而当裂纹间距比较大时,试样破坏模式在张拉破坏的几种模式之间转变;随着裂纹间距的变大,试样由剪切破坏向张拉破坏转变;随着裂纹未连通率变化,试样破坏模式主要在张拉破坏的几种模式之间转变。②分析在不同空间分布下试样的应力-应变曲线,考虑了裂纹的空间布置因素对试样力学特性的影响:随着裂纹倾角的变大,试样的起裂应力有先减小后增大的,也有一直增大的,而峰值应力有先增大后减小的,也有一直增大的;随着裂纹间距的变大,试样的起裂应力和峰值应力都是先减小后增大;随着裂纹未连通率变小,试样的起裂应力和峰值应力都是先减小后增大。③根据试样破坏过程中的声发射数据和应力应变曲线,分析每个试样破坏过程中的声发射特征,得到如下结论:剪切破坏模式中产生声发射事件的水平比较低,其变化趋势与应力应变曲线基本一致;张拉破坏模式中产生声发射事件的水平比较高,其变化趋势与应力应变曲线有较大的不同。④通过观察试样的位移矢量图和数值模拟结果,分析了裂纹起裂和试样破坏时的位移变化情况,得到如下结论:起裂时,试样变形一般以压缩变形为主,试样一般有向下方移动的趋势;破坏时,试样表面位移改变比较大,有明显的相对滑移现象;根据裂纹空间布置的不同,相对滑移面沿主对角线或副对角线。
[Abstract]:Because of the complex geological structure and occurrence conditions, rock is a typical discontinuous medium, which has some internal defects such as mineral cleavage, microcracks, intergranular voids, lattice defects and so on. Through a large number of studies at home and abroad, it is found that under the condition of force, these weak structural planes will open, expand and pass through, which will lead to rock instability and even destruction. Therefore, it is of great significance for practical engineering to study the similar model test of specimens with precast cracks. A lot of research work has been done on the specimens with two precast cracks, but the influence of the spatial arrangement on the failure process of the specimens has not been considered synthetically. In order to study the effect of crack space arrangement on fracture initiation mode, failure mode, specimen mechanical properties and surface displacement, Based on the acoustic emission and image processing techniques, the following works have been done and corresponding results have been obtained: 1. The sequence of microcracks at the tip of prefabricated cracks is described, and the types of new cracks are classified as airfoil cracks. Secondary coplanar crack and secondary inclined crack. The effect of the space arrangement of the crack on the initiation mode and the failure mode is considered. With the increase of the dip angle of the crack, when the crack spacing is small, the failure mode of the specimen changes from shear failure to tensile failure, and when the crack spacing is large, the fracture mode changes from shear failure to tensile failure. The fracture mode of the specimen changes between several modes of tensile failure; with the increase of crack spacing, the specimen changes from shear failure to tensile failure; and with the change of crack unconnectivity, The failure mode of specimens is mainly transformed between several modes of tensile failure. 2. The stress-strain curves of specimens with different spatial distributions are analyzed. The effect of the space arrangement of the crack on the mechanical properties of the specimen is considered. With the increase of the crack inclination angle, the initial crack stress of the specimen decreases first and then increases, and the peak stress increases first and then decreases. With the increase of crack spacing, the crack initiation stress and peak stress of the specimen decrease first and then increase; with the crack unconnected ratio becoming smaller, the crack initiation stress and the peak stress increase with the increase of crack spacing. The initial crack stress and peak stress of the specimen are reduced first and then increased .3 according to the acoustic emission data and the stress-strain curve during the failure process of the specimen, the characteristics of the acoustic emission in the failure process of each specimen are analyzed. The conclusions are as follows: the level of acoustic emission events in shear failure mode is relatively low, and the variation trend is basically consistent with the stress-strain curve, and the level of acoustic emission events in tensile failure mode is relatively high. The variation trend is quite different from the stress-strain curve. 4 by observing the displacement vector diagram and the numerical simulation results of the specimen, the variation of the displacement during the crack initiation and the specimen failure is analyzed, and the following conclusions are obtained: when the crack starts, The deformation of the specimen is mainly compression deformation, and the specimen tends to move downwards. During the failure, the surface displacement of the specimen changes greatly and there is obvious relative slip phenomenon. According to the different space arrangement of the crack, the deformation of the specimen is mainly compressed, and the specimen tends to move downwards. The relative slip surface is along the main diagonal line or the secondary diagonal line.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU45

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