节理岩体变形参数波动法测试及黏性系数非定常特性

发布时间：2018-01-23 01:49

本文关键词： 位移不连续模型临界厚度频散特性黏性衰减参数正演　出处：《江西理工大学》2017年硕士论文　论文类型：学位论文

【摘要】：为快捷获取岩土体岩性参数,在德兴铜矿、双旗山金矿采空区选取岩体发育较好、岩性完整的边坡面进行波动法现场测试,研究应力波在节理岩体中的传播规律,基于波形变化测试岩体变形参数,并与钻孔弹模仪的测试结果进行比较,研究结果如下:(1)将节理面视为Kelvin黏弹性介面,考虑节理质量对应力波传播的影响,运用波的位移位函数得到谐波在厚黏弹性节理的透、反射系数计算公式,采用波形相关系数描述子波穿过黏弹性节理的波形变化,讨论具有一定厚度的黏弹性节理采用位移不连续模型计算的适用条件。设厚黏弹性节理模型和位移不连续模型的透射波波形相关系数为0.9时对应的节理厚度为临界厚度。采用简化的位移不连续模型描述岩体节理面,基于波形变化系数最小的原则,确定节理面力学参数行之有效的方法。岩体与节理的阻抗比对临界厚度的影响很小;临界厚度随子波中心频率增大成负指数减小;入射角越大,临界厚度随中心频率减小得越慢。当节理厚度为0.03m时,采用位移不连续模型和厚黏弹性模型计算得到节理力学参数非常接近;随节理厚度和子波中心频率增加,运用位移不连续模型的计算结果偏差越大。实验结果与理论分析是一致的。(2)岩体黏滞性作用对应力波传播影响主要体现为速度频散和幅值衰减两方面。前者体现为应力波传播相速度因频率而变化,将岩体视为Kelvin黏弹性介质,运用傅立叶级数对测点实测波形进行展开,根据应力波传过黏弹性岩体时相位的变化特征,来研究相速度的频散特性。其中,级数展开时,谐波次数对波形分解影响极大,取n=300足够满足计算需要。假设介质黏性系数非定常的表达:η=a0f q,基于P波的传播规律计算得到参数a0=1007600,q=0.136,当频率f=300Hz时,计算得到黏性系数η=2.189MPa?s;基于SV波的传播规律计算得到参数a0=702861,q=0.321,当频率f=300Hz时,计算得到黏性系数η=4.386MPa?s。(3)将岩体介质视为Kelvin半无限体,根据应力波黏性衰减理论,拟合P波振幅随传播距离的衰减系数,计算得到岩体弹性模量为E=3.27GPa;拟合SV波振幅随传播距离的衰减系数,计算得到岩体弹性模量为E=3.22GPa;采用钻孔弹模仪测试得到岩体弹性模量为2.46GPa,动力法测试岩体弹性模量是静力法1.33倍。假设介质黏性系数非定常的表达:η=a0f q,基于P波的传播规律计算得到岩体黏性系数初值a0=7341,陡度参数q=0.509;基于SV波传播规律计算得到初值系数a0=315000.8,陡度参数q=0.249。
[Abstract]:In order to obtain the lithologic parameters of rock and soil quickly, the rock mass developed well in the goaf of Shuangqishan Gold Mine is selected in Dexing Copper Mine, and the slope surface with intact lithology is tested by wave method. The propagation law of stress wave in jointed rock mass is studied, and the deformation parameters of rock mass are measured based on waveform change, and the results are compared with those of borehole elastic modulus meter. The results are as follows: (1) considering the effect of the mass of the joint on the propagation of force wave, the harmonic permeation of thick viscoelastic joints is obtained by using the displacement potential function of the wave, which regards the joint surface as the Kelvin viscoelastic interface, and considers the effect of the mass of the joint on the propagation of the force wave. The wave correlation coefficient is used to describe the waveform change of wavelet passing through viscoelastic joints. The suitable conditions for calculating viscoelastic joints with certain thickness by displacement discontinuity model are discussed. The thickness of joints corresponding to thick viscoelastic joint model and displacement discontinuity model is given when the correlation coefficient of transmission wave waveform is 0.9. For critical thickness, a simplified discontinuous displacement model is used to describe the joints of rock mass. Based on the principle of minimum waveform variation coefficient, an effective method for determining mechanical parameters of joints is proposed. The impedance ratio of rock mass to joint has little effect on critical thickness. The critical thickness decreases exponentially with the increase of the center frequency of the wavelet. When the thickness of joints is 0.03m, the mechanical parameters of joints obtained by displacement discontinuity model and thick viscoelastic model are very close. It increases with the thickness of joints and the frequency of wavelet center. The greater the deviation of the calculated results from the discontinuous displacement model is, the more consistent the experimental results are with the theoretical analysis. The effect of viscous rock mass on wave propagation is mainly reflected in two aspects: velocity dispersion and amplitude attenuation. The former shows that the phase velocity of stress wave varies with frequency. The rock mass is regarded as a Kelvin viscoelastic medium, and the measured waveform is expanded by Fourier series, and the phase change characteristics of the viscoelastic rock mass are obtained according to the stress wave propagation over the viscoelastic rock mass. In order to study the dispersion characteristics of phase velocity, the number of harmonics has a great influence on the waveform decomposition when the series is expanded. If the unsteady expression of the viscosity coefficient of the medium is assumed: 畏 _ 0 a _ 0f _ Q, the parameter a _ (0) _ (1007600) is calculated based on the propagation law of P wave. When the frequency is 300 Hz, the viscosity coefficient 畏 is calculated to be 2. 189 MPa? Based on the propagation law of SV wave, the parameter a0o / 702861QN / 0.321 is obtained, and the viscosity coefficient 畏 = 4.386MPa / a is calculated when the frequency is 300 Hz. According to the theory of stress wave viscosity attenuation, the attenuation coefficient of P wave amplitude with propagation distance is fitted. The elastic modulus of rock mass is calculated to be E ~ (3. 27) GPA; By fitting the attenuation coefficient of SV wave amplitude with propagation distance, the elastic modulus of rock mass is calculated to be E ~ (3. 22) GPA; The elastic modulus of rock mass measured by borehole elastic modulus instrument is 2.46 GPA, and the elastic modulus of rock mass measured by dynamic method is 1.33 times that of static method. Based on the propagation law of P-wave, the initial value of viscosity coefficient of rock mass, a _ 0 ~ 7341, and the steepness parameter Q ~ (0.509) are obtained. Based on the propagation law of SV wave, the initial coefficient a015000.8 and the steepness parameter qn 0.249 are obtained.
【学位授予单位】：江西理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU45

【参考文献】