类岩石节理岩体损伤断裂试验研究

发布时间：2018-08-16 16:39

【摘要】：节理裂隙作为自然界岩体的构造缺陷之一,其构造特征以及物理力学性质影响和决定着整个岩体的物理力学特性。节理岩体损伤断裂机制探究,是目前岩石力学界最前沿的研究方向,也是岩体工程中急需解决的难题。为了研究节理岩体单轴压缩条件下的断裂损伤破坏机制,采用水泥砂浆试验材料,通过预制节理法制备类岩石模型试件,再利用WAW-1000C微机控制电液伺服机对养护好的试件进行单轴分级加载压缩试验。压缩过程中借助ZBL-U520非金属超声波检测仪对试件进行波速测试,记录不同荷载下超声波速,同时通过PTS-C10裂纹测宽仪测量节理裂缝宽度,记录不同荷载下部分节理裂缝宽度的变化。同时在整个加载过程中采用高速摄像设备观察、记录试件节理表面新生裂纹的萌发,扩展和贯通过程。得到主要结论如下:(1)岩体滑动裂纹模型理论对单轴压缩下节理尖端起裂分析是适用的,能够很好的解释实验节理起裂现象,累积损伤理论也能很好的反应试验中超声波速的衰减规律。(2)单轴加载压缩过程中,节理尖端部会萌生出包括翼型裂纹、次生倾斜裂纹和次生共面裂纹三大类新生细裂纹,但是并不是所有节理尖端都会萌生新裂纹,同时在试件边界位置处会有贯穿整个试件的张拉裂纹产生。就裂纹出现先后而言,张拉裂纹一般出现较早,对于节理尖端裂纹起裂先后,最早为翼型裂纹,次生共面裂纹出现较晚。但也有与翼型裂纹同时出现的情况,而次生倾斜裂纹一般在翼型裂纹之后出现。对于含三条非连续节理的试件,加载工程中节理间往往会发生搭接现象,但参与连接的裂纹数量、位置以及连接的类型会因几何分布的变化有较大的差异,总体上呈现出张拉、剪切和拉剪复合三种连接模式,并且只含竖向和水平节理的试件仅出现了张拉与拉剪复合连接,没有出现剪切裂纹连接模式,说明裂纹的几何分布对连接模式有较大的影响。(3)由于试件节理条数以及几何空间分布的不同,应力应变曲线的走势规律会相差很大,并且应力峰值、残余应力、峰值出现时应变等都会存在明显的差异,但是曲线后期变化都呈现脆性破坏曲线特性,同时比较节理起裂应力值,发现水平节理起裂时应力比竖向节理起裂时应力要小,比倾斜节理起裂时要大,尖端离试件边界越近,起裂应力值越小;而对于倾角变化对启裂应力的影响,则没有表现出明显的规律。对于含两条节理或是三条节理的试件,总体上只含有的竖向、水平节理的试件比含有倾斜节理的试件的抗压强度更高,压缩下稳定性更好。(4)比较分析各试件荷载下波速变化特性,得出在对试件施加荷载前,试件的超声波速随节理条数及几何空间分布存在差异,但在同类试件中随节理倾角、夹角的变化存在一定规律。对试件加荷载后,波速随荷载增大而呈下降衰减趋势。总体相同荷载下波速在含有倾斜节理试件中的衰减最大,在只含平行、竖向节理试件中衰减较小。同时波速出现大幅下降时的荷载及下降幅度与试件节理类型及组合形式关系密切。
[Abstract]:As one of the structural defects of natural rock mass, the structural characteristics and physical and mechanical properties of jointed rock mass affect and determine the physical and mechanical properties of the whole rock mass. Fracture damage and failure mechanism under uniaxial compression were studied. Rock-like model specimens were prepared by precast joint method with cement mortar test materials. The cured specimens were subjected to uniaxial stepwise compression test by WAW-1000C microcomputer controlled electro-hydraulic servo machine. The ultrasonic velocity was measured under different loads, and the crack width was measured by PTS-C10 crack width meter to record the changes of crack width under different loads. The main conclusions are as follows: (1) Rock mass sliding crack model theory is applicable to the analysis of crack initiation at the tip of joints under uniaxial compression, which can well explain the phenomenon of crack initiation and accumulative damage theory can also well reflect the attenuation law of ultrasonic velocity in the test. (2) During uniaxial compression, the tip of joints will germinate including wings. There are three kinds of new fine cracks, i.e. mode crack, secondary inclined crack and secondary coplanar crack. But not all joint tips will produce new cracks, and tensile cracks will occur throughout the specimen at the edge of the specimen. Secondary coplanar cracks occur later than airfoil cracks, but they also occur at the same time as airfoil cracks. Secondary inclined cracks usually occur after airfoil cracks. The types of joints vary greatly due to the variation of geometric distribution. Generally speaking, there are three kinds of joint modes: tension, shear and tension-shear. Moreover, only the vertical and horizontal joints appear tension-shear composite connection, and there is no shear crack connection mode. This shows that the geometric distribution of cracks has a great influence on the connection mode. (3) The trend of stress-strain curves varies greatly due to the number of joints and the geometric and spatial distribution of the joints, and there are obvious differences in peak stress, residual stress and strain when the peak occurs. However, the later changes of the curves all show the characteristics of brittle failure curve, and the crack initiation stress values are compared and the level is found. The stress at the beginning of cracking is smaller than that at the beginning of vertical cracking, and larger than that at the beginning of inclined cracking. The nearer the tip is to the boundary of the specimen, the smaller the value of initiation stress is; however, there is no obvious rule for the effect of inclination on initiation stress. The compressive strength and stability of flat joint specimens are higher than those of inclined joint specimens. (4) Comparing and analyzing the variation characteristics of wave velocity under load, it is concluded that the ultrasonic velocity of flat joint specimens varies with the number of joints and geometric space distribution before loading, but with the inclination angle and angle of joints in the same specimens. After loading, the wave velocity decreases with the increase of load. In general, the wave velocity decreases most in the specimens with inclined joints under the same load, but less in the specimens with parallel and vertical joints. The form of combination is closely related.
【学位授予单位】：南华大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TU45

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