不同张开度裂纹扩展的模型试验研究

发布时间：2018-03-22 23:32

本文选题：类岩石材料　切入点：裂纹张开度　出处：《重庆大学》2014年硕士论文　论文类型：学位论文

【摘要】：由于构造应力场的长期作用，岩石不是均质的，而是由许多节理、裂纹、断层、滑动面等构成的非均质各向异性结构体。根据国内外的研究并结合工程实践可知，含裂纹岩体的失稳和破坏都是通过岩体内部裂纹的张开、扩展而产生的贯通滑移面所引起的。因此通过在类岩石材料试样中预制原始裂纹进行相似模型试验研究有重要的工程指导意义。很多学者对含两根不同空间分布裂纹试样的研究做了很多工作，但并未考虑裂纹张开度对裂纹起裂、扩展、贯通以及岩体破坏的影响。本文为了探究裂纹张开度对裂纹起裂应力、起裂模式、扩展路径、贯通模式以及岩体强度和应力应变的影响，主要做了以下工作并取得了相应成果： ①结合实验目的及实验条件，进行了实验方案的设计。确定试样尺寸并制作模具，设置了三种原始裂纹张开度，分别为0.5mm、1mm、2mm，，同时设置五种不同的裂纹空间分布。利用HG100K高速动态分析系统对试样加载过程进行图像采集，并记录了裂纹起裂、扩展、贯通的整个过程。利用CMT5504电子万能试验机对试样进行单轴压缩，通过微机系统获得了相应的试验数据。 ②新生裂纹类型主要有翼形裂纹、次生共面裂纹和次生倾斜裂纹三种。裂纹张开度对裂纹起裂模式的影响表现为：随着裂纹张开度的增大，其新生裂纹类型增多，新生裂纹的数量也随之增加。裂纹张开度不变时，裂纹倾角对裂纹起裂模式的影响表现为：随着裂纹倾角的增大，其新生裂纹类型增多。 ③裂纹张开度对裂纹贯通模式的影响主要有三种情况：随着裂纹张开度的增大，1）试样的破坏逐渐由单纯的剪切破坏转变为由张拉破坏面和剪切破坏面贯通所致的破坏；2）试样的破坏逐渐由翼形裂纹和次生倾斜裂纹贯通破坏转变为翼形裂纹和次生共面裂纹贯通破坏；3）而在翼形裂纹相互搭接贯通的张拉破坏模式下，裂纹张开度对其几乎没有影响。裂纹张开度相同时，裂纹倾角对裂纹贯通模式的影响表现为：试样的破坏逐渐由翼形裂纹和次生倾斜裂纹贯通破坏转变为剪切破坏。 ④裂纹张开度对试样力学特性有较明显影响，即随着张开度的增加：试样的峰值强度逐渐减小；试样的起裂应力逐渐增大，试样在峰值强度后更容易起裂；试样的极限应变逐渐减小。同时，裂纹张开度越大，试样应力-应变曲线中，峰值强度后试样的应力减小得越快，残余变形量也越小。
[Abstract]:Because of the long-term action of the tectonic stress field, the rock is not homogeneous, but is composed of many joints, cracks, faults, sliding surfaces and other heterogeneous anisotropic structures. The instability and failure of cracked rock mass are through the opening of cracks inside the rock mass. Therefore, it is of great significance to study the similar model test of prefabricated original cracks in rock-like material samples. Many scholars have studied two different spatial distributions. A lot of work has been done in the study of cracked specimens. However, the effect of crack opening on crack initiation, propagation, penetration and rock mass failure is not considered. Through the model and the impact of rock mass strength and stress and strain, the main work has done the following and achieved the corresponding results:. 1. According to the experimental purpose and experimental conditions, the experimental scheme is designed. The sample size is determined and the mould is made, and three kinds of original crack opening degree are set up. At the same time, five different kinds of crack spatial distribution are set up. The images of the specimen loading process are collected by HG100K high-speed dynamic analysis system, and the crack initiation and propagation are recorded. Uniaxial compression of the sample was carried out by using CMT5504 electronic universal testing machine, and the corresponding test data were obtained by microcomputer system. (2) the main types of new crack are wing crack, secondary coplanar crack and secondary inclined crack. The effect of crack opening on crack initiation mode is as follows: with the increase of crack opening, the new crack type increases. When the crack opening degree is constant, the effect of crack inclination on crack initiation mode is as follows: with the increase of crack inclination, the type of new crack increases. (3) the influence of crack opening degree on crack through-through mode is mainly threefold: with the increase of crack opening degree, the failure of specimen gradually changes from simple shear failure to tensile failure plane and shear failure surface transfixion. The failure of the specimen is gradually changed from the wing crack and the secondary inclined crack to the wing crack and the secondary coplanar crack. When the crack opening degree is the same, the effect of crack inclination angle on crack through-through mode is shown as follows: the failure of specimen is changed from wing crack and secondary inclined crack through failure to shear failure. (4) the crack opening degree has obvious influence on the mechanical properties of the specimen, that is, with the increase of the opening degree, the peak strength of the specimen decreases gradually, the initiation stress of the specimen increases gradually, and the specimen starts to crack more easily after the peak strength. At the same time, the larger the crack opening degree is, the faster the stress decreases after the peak strength and the smaller the residual deformation in the stress-strain curve.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU45

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