三轴应力下岩石剪切破裂的声发射特征及破裂面形态分析

发布时间：2018-07-01 11:18

本文选题：岩石剪切 + 声发射　；参考：《太原理工大学》2017年硕士论文

【摘要】：岩石是一种由多种矿物质组成的不均质体,因此岩石的性质较为复杂。岩石的破坏情况在自然界以及工程中较难预测,本文通过施加三轴应力条件,研究岩石剪切变形破坏过程中的声发射峰值频率特征、逾渗特征、以及表面不平整度特征,来寻求一些岩石剪切破坏的敏感指标。采用大型真三轴试验机对花岗岩和石灰岩进行双面剪切试验和单面剪切试验,结合声发射仪器采集试验过程中的声学信号,获取花岗岩双面剪切全过程中的剪切应力-时间特征曲线及声发射参数-时间特征曲线。分析施加不同法向和侧向应力时,等速剪切变形破坏过程的声发射峰值频率变化特征。试验结果表明:法向应力的改变会引起破坏形式的不同(稳态破坏与失稳破坏),从而引起峰值频率特征的差异;侧向应力的改变对峰值频率特征无明显影响;剪切过程中的声发射峰值频率可分为波动期、上升期、波动期、下降期和稳定期;峰值频率能够大致反映出岩石的破坏临界点位置,可以作为反映花岗岩剪切破坏情况的一项指标。峰值频率变化特征还可以反映出破坏过程中剪应力的变化情况。分析剪切破坏过程中的逾渗特征,发现事件的连通率C能够作为判断岩石破坏的依据。在花岗岩双面剪切破坏过程中,当事件的空间占有率达到60%至65%时,剪应力达到最大值,花岗岩发生稳态破坏或失稳破坏;在花岗岩和石灰岩的单面剪切破坏过程中,当事件的空间占有率达到55%至60%时,剪应力达到最大值,岩石试样发生破坏。能量的累积增长速率也可作为判断岩石破坏的依据,剪切破坏过程中,弹性变形和弹塑性变形阶段,能量累积值的增长速率较快;剪应力峰值之后岩样发生破坏,能量累积值增长速率明显降低。表面不平整度是表面微观几何形状误差的表征形式,本文从表面不平整度的高度参数(轮廓的平均算术偏差Rsa、轮廓的不平度平均高度Rsz、以及轮廓最大高度Rsy)角度研究剪切破裂面的形貌特征。发现在花岗岩的双面剪切破坏和单面剪切破坏过程中,法向应力值越大,Rsa、Rsz、以及Rsy的值越小;侧向应力值对Rsa、Rsz、以及Rsy的值均无明显影响;在石灰岩的单面剪切破坏过程中,法向应力值越大,Rsa、Rsz、以及Rsy的值越小。
[Abstract]:Rock is a kind of heterogeneous material composed of many minerals, so the properties of rock are more complicated. The failure of rock is difficult to predict in nature and engineering. By applying triaxial stress condition, the characteristics of acoustic emission peak frequency, percolation and surface irregularity during shear deformation failure of rock are studied in this paper. To find some sensitive indicators of rock shear failure. A large true triaxial testing machine was used to carry out double and single side shear tests on granite and limestone, and acoustic signals were collected by acoustic emission instrument. The shear stress-time characteristic curve and acoustic emission parameter-time characteristic curve were obtained during the whole process of two-sided shear of granite. The characteristics of peak frequency variation of acoustic emission in the process of constant velocity shear deformation failure are analyzed when different normal and lateral stresses are applied. The experimental results show that the change of normal stress will lead to different failure forms (steady state failure and instability failure), which will lead to the difference of peak frequency characteristics, while the change of lateral stress will not have obvious effect on the peak frequency characteristics. The peak frequency of acoustic emission in shear process can be divided into three periods: fluctuation period, rising period, fluctuation period, descending period and stable period, and the peak frequency can roughly reflect the critical point position of rock failure. It can be used as an index to reflect the shear failure of granite. The change of peak frequency can also reflect the variation of shear stress during failure. By analyzing the percolation characteristics during shear failure, it is found that the connectivity C of events can be used as a basis for judging rock failure. In the process of two-sided shear failure of granite, when the space occupation of the event reaches 60% to 65%, the shear stress reaches the maximum, and the steady failure or instability of the granite occurs, and in the process of one-sided shear failure of granite and limestone, When the space occupation of the event reaches 55% to 60%, the shear stress reaches the maximum value and the rock specimen is destroyed. The accumulative growth rate of energy can also be used as a basis for judging rock failure. During shear failure, the growth rate of energy accumulation value is faster in the stage of elastic deformation and elastic-plastic deformation, and the rock sample is destroyed after the peak shear stress. The growth rate of energy accumulation value decreased obviously. Surface irregularity is the representation of surface micro-geometric error. In this paper, the morphology of shear fracture surface is studied from the angle of height parameters of surface irregularity (mean arithmetic deviation of contour Rsa, mean height of roughness of contour Rsz, and maximum height of contour Rsy). It is found that the greater the normal stress value and the smaller the Rsy value during the two-sided shear failure and the one-sided shear failure of granite, the less the lateral stress value has on Rsao Rsz and Rsy values, and in the one-sided shear failure process of limestone, the lateral stress value has no obvious effect on Rsao Rsz and Rsy values. The greater the normal stress value is, the smaller the value of Rsao Rsz and Rsy is.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD315

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