Damaged rock mass contains a great number of microstructures and defects at various scales, which could influence wave propagation significantly. In this paper, investigation of low-amplitude stress wave attenuation in rocks with different damage degrees was undertaken to determine the effects of parameters including damage degree, heterogeneity and type of waveforms on wave propagation, attenuation and slowness. The numerical method was validated through comparison with laboratory measurements. The damage was induced by conducting uniaxial compression tests on the intact rocks and was defined with the acoustic emission. The results showed that the attenuation ratio of low-amplitude stress wave increases with increasing rock damage degree. The rock heterogeneity was incorporated into the numerical model using a digital image processing technique with the combination of X-ray micro-computerized tomography. We found that the rock heterogeneity has great influence on the wave amplitude attenuation. Three types of waveforms, i.e., half-sine wave, square wave and exponential decay wave, were utilized to analyze influences of waveforms on attenuation characteristics in damaged rock specimens. The attenuation ratio of the exponential decay wave is the highest for rock specimens with the same damage degree, attributed to its highest dominant frequency. Moreover, detailed spectrum analysis suggested that the dominant frequency of the wave signal decreases with increasing damage degree. Based on derived simulating results, an improved classification scheme for determining rock fracturing degree, which groups the rock into zones of slightly fractures, moderately fractured and strongly fractured, was established by considering the relationship between wave amplitude and damage, since wave amplitude, other than wave velocity, is more sensitive to rock damage. The findings in this paper could facilitate a better understanding of wave propagation through rock and provide another means to determine rock fracturing degree.

中文翻译：

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损伤岩石的低振幅波传播衰减及岩石破裂程度分级方案

受损岩体含有大量不同尺度的微观结构和缺陷，对波的传播有显着影响。本文通过对不同损伤程度岩石低幅应力波衰减的研究，确定损伤程度、非均质性和波形类型等参数对波的传播、衰减和慢度的影响。数值方法通过与实验室测量值的比较得到验证。损伤是通过对完整岩石进行单轴压缩试验引起的，并用声发射来定义。结果表明，低幅应力波的衰减率随着岩石损伤程度的增加而增大。使用数字图像处理技术与 X 射线微计算机断层扫描相结合，将岩石非均质性纳入数值模型。我们发现岩石的非均质性对波幅衰减有很大的影响。利用半正弦波、方波和指数衰减波三种波形，分析了波形对损伤岩石试样衰减特性的影响。指数衰减波的衰减率在相同损伤程度的岩石标本中最高，这归因于其最高的主频率。此外，详细的频谱分析表明，波信号的主频随着损坏程度的增加而降低。根据导出的模拟结果，由于波幅比波速更敏感，考虑波幅与损伤的关系，建立了一种改进的确定岩石破裂程度的分类方案，将岩石分为微裂缝、中裂缝和强裂缝区域。岩石损坏。本文的研究结果有助于更好地理解波在岩石中的传播，并提供另一种确定岩石破裂程度的方法。