Abstract To study the time-varying dominant frequency distribution characteristics during the cracking process of intact and flawed rocks, uniaxial compression tests are carried out on three types of red sandstone specimens. Both acoustic emission (AE) and photographic technologies are performed to monitor the real-time cracking process of tested specimens. The relationship between the AE rate curve, the axial stress-time curve and the cracking process is first analyzed, which can be employed to evaluate the microscopic and macroscopic deformation characteristics of rocks. The time-varying dominant frequency and amplitude distribution characteristics in different cracking stages of tested rocks are investigated. Four modes of AE signals, i.e., AE signals with low-frequency and high-amplitude (LF-HA), AE signals with low-frequency and low-amplitude (LF-LA), AE signals with intermediate-frequency and low-amplitude (IF-LA) and AE signals with high-frequency and low-amplitude (HF-LA), are found. The coupling application of four modes of AE signals extracted from unstable deformation stages can be viewed as early warning for unstable failure of rocks. The fracture mechanism of intact and flawed rocks is discussed based on the statistical characteristics of dominant frequency during the cracking process. Micro-shear cracking mainly dominants the ultimate failure of all of tested rocks.

中文翻译：

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缺陷红砂岩破裂过程中的时间主导频率演化特征

摘要 为研究完整和有缺陷岩石开裂过程中时变主频分布特征，对三种红砂岩试件进行了单轴压缩试验。使用声发射 (AE) 和摄影技术来监控测试样品的实时开裂过程。首先分析了声发射速率曲线、轴向应力-时间曲线与开裂过程之间的关系，可用于评价岩石的微观和宏观变形特征。研究了受试岩石不同开裂阶段的时变主导频率和振幅分布特征。AE信号的四种模式，即低频高振幅AE信号（LF-HA），找到了低频低幅度AE信号（LF-LA）、中频低幅度AE信号（IF-LA）和高频低幅度AE信号（HF-LA） . 从不稳定变形阶段提取的四种声发射信号的耦合应用可以看作是岩石不稳定破坏的预警。基于开裂过程中主频的统计特征，讨论了完整和有缺陷岩石的断裂机制。微剪切开裂在所有被试岩石的最终破坏中占主导地位。从不稳定变形阶段提取的四种声发射信号的耦合应用可以看作是岩石不稳定破坏的预警。基于开裂过程中主频的统计特征，讨论了完整和有缺陷岩石的断裂机制。微剪切开裂在所有被试岩石的最终破坏中占主导地位。从不稳定变形阶段提取的四种声发射信号的耦合应用可以看作是岩石不稳定破坏的预警。基于开裂过程中主频的统计特征，讨论了完整和有缺陷岩石的断裂机制。微剪切开裂在所有被试岩石的最终破坏中占主导地位。