基于矩张量的岩石破裂微观机制声发射研究

发布时间：2018-04-15 02:26

本文选题：声发射 + 矩张量　；参考：《成都理工大学》2017年硕士论文

【摘要】：岩石是典型的各向异性的脆性材料。随着外荷载的增加,岩石内部微裂纹萌生演化、扩展和贯通直至形成宏观破裂面。声发射采集技术可以不间断、实时地监测岩石材料内部微破裂的萌生和发展,从而推演出试样内部的形变、破裂失稳过程和力学机制。目前,声发射在声发射参数分析、频谱特征解读,空间三维定位等方面有较好的运用。然而要研究岩石破裂微观机制,只得到微破裂在时间和空间上的演化过程是不足的,还需要从力学性质上对微破裂的张拉、剪切滑移进行分类,进而深入了解微裂纹间相互作用和扩展、贯通机制。为矿山微震监测、隧道稳定、深部变形破裂成因机理研究奠定基础,也为岩石失稳破坏预测提供依据。因此,从室内试验出发设计压缩试验(巴西劈裂、单轴压缩实验、Z型剪切实验、含预制裂隙压缩实验)并进行同步声发射采集。运用矩张量程序分析微裂纹震源机制(破裂类型、破裂几何参数)、破裂能,结合应力应变曲线和声发射参数,分析不同破坏阶段下岩石微破裂性质和能量演化特征,从微观角度解释岩石破裂演化过程。得到以下几点结论:(1)基于AR-AIC和单纯形法(Simplex),自行编写声发射点定位解算程序,并通过断铅实验验证算法的定位精度。得出:破裂点在探头阵列内时,定位误差在10mm以内,阵列之外定位误差在15mm左右。(2)将AE幅度(AMP)和与空间定位结合,绘出AMP空间分布图,可看出主破裂面的形成和集中,能有效排除无效声发射点的干扰(低能量、低幅度,离散的声发射事件点)。(3)基于弹性波动力学理论,依据M.ohstu矩张量解法,自行编写MATLAB矩张量求解程序,并设计实验验证程序正确性。得出:“Z”型试件压缩实验中,JQ2在切口处呈压缩拉伸破裂,G2在中间梁处出现剪切破裂。矩张量计算结果得出JQ2张剪比例为51%、29%,G2张剪比例为77%、19%,与宏观破裂一致,证明了矩张量程序在震源机制分析中的准确性和适用性。(4)巴西实验中,矩张量程序分析得出张拉裂纹、剪切裂纹和混合裂纹的平均比例约为59%、30%、11%。可见,巴西劈裂实验中张拉裂纹起到主导作用,剪切裂纹则起到了加速和促进作用。证明了巴西劈裂实验虽然与直接拉伸试验应力场分布不同,起裂点不同,但其震源机制(张拉占据主导作用)一致,因此其用来测试试样的抗拉强度是合理的。(5)张拉能、剪切能和混合能在岩石破裂过程中比例和演化规律与张剪切裂纹较为接近,呈对应关系。岩石总体呈张拉型破裂时,张拉能占比较高,反之在剪切试件中,剪切能占比较高。应力加载中,破裂能主要集中于裂纹密集出现时或是大破裂(大事件)发生时,集中在80-100%应力阶段出现能量剧增现象。
[Abstract]:Rock is a typical anisotropic brittle material.With the increase of the external load, the microcracks in the rock initiate and evolve, propagate and penetrate until the macroscopic fracture surface is formed.Acoustic emission acquisition technique can monitor the initiation and development of micro-fracture in rock material in real time and deduce the deformation, fracture instability process and mechanical mechanism.At present, acoustic emission has a good application in acoustic emission parameter analysis, spectrum feature interpretation, spatial three-dimensional positioning and so on.However, in order to study the micromechanism of rock fracture, it is insufficient to obtain only the evolution process of microfracture in time and space, and it is necessary to classify the tensioning and shear slip of microfracture in terms of mechanical properties.Furthermore, the mechanism of microcrack interaction and propagation is deeply understood.It lays a foundation for the study of the formation mechanism of mine microseismic monitoring, tunnel stability and deep deformation and fracture, and also provides the basis for the prediction of rock instability and failure.Therefore, the compression test (Brazilian split, uniaxial compression test, Z-type shear test, including prefabricated fracture compression test) is designed and the synchronous acoustic emission acquisition is carried out.The focal mechanism of microcrack (rupture type, fracture geometry parameter, fracture energy, stress-strain curve and acoustic emission parameter) are analyzed by using the moment Zhang Liang program, and the characteristics of microfracture and energy evolution in different failure stages are analyzed.The process of rock fracture evolution is explained from the microscopic point of view.The following conclusions are obtained: (1) based on AR-AIC and simplex method, the program of acoustic emission location is written by ourselves, and the accuracy of the algorithm is verified by the experiment of lead break.It is concluded that when the rupture point is in the probe array, the positioning error is within 10mm, and the positioning error outside the array is about 15mm. (2) combining AE amplitude with spatial positioning, the spatial distribution map of AMP can be drawn, and the formation and concentration of the main rupture surface can be seen.Based on the theory of elastic wave mechanics and the M.ohstu moment Zhang Liang solution, we can effectively eliminate the interference of invalid acoustic emission points (low energy, low amplitude, discrete acoustic emission event point) and write the MATLAB moment Zhang Liang solution program by ourselves, based on the theory of elastic wave mechanics and the M.ohstu moment Zhang Liang solution.Experiments are designed to verify the correctness of the program.It is concluded that in the compression test of "Z" type specimen, the compression tensile fracture of JQ2 at the notch and the shear rupture of the G-2 at the middle beam are observed.The result of Zhang Liang's calculation shows that the ratio of JQ2 tensioning and shearing is 51 / 29/ G2, which is consistent with the macroscopic rupture, which proves the accuracy and applicability of the moment Zhang Liang program in the analysis of the focal mechanism.) in the Brazilian experiment, the moment Zhang Liang program analysis shows the tension crack.The average ratio of shear crack to mixed crack is about 59%.It can be seen that tensile crack plays a leading role and shear crack accelerates and accelerates in Brazilian splitting experiment.It is proved that although the stress field distribution and fracture initiation point of Brazilian splitting test are different from that of direct tensile test, the focal mechanism (tensioning dominates) is the same, so the tensile strength of the test specimen is reasonable.The ratio and evolution of shear energy and mixed energy in the process of rock fracture are close to those of tensile shear crack.When the rock is tension-type fracture, the tensile energy is higher, whereas in the shear specimen, the shear energy is higher.In the stress loading, the fracture energy is mainly concentrated at the time when the crack is dense or when the big rupture (big event) occurs, and the phenomenon of energy surge occurs in 80-100% stress stage.
【学位授予单位】：成都理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU45

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