The abrupt rock-related hazards, such as landslide, rock burst, and collapse, seriously threaten the safety and service life of engineering works. Precursory information on critical transitions preceding sudden fracture is of great significance in rock mechanics and engineering. This study investigates the critical slowing down feature of acoustic emission (AE) signals and precursory indicators during the mode I fracture process of brittle rock. Cracked chevron notched Brazilian disc (CCNBD) specimens were utilized, accompanied by acoustic emission monitoring. The principle of critical slowing down was introduced to study AE count sequences, and the variance and autocorrelation coefficient versus loading time curves were analyzed. The results show critical slowing down phenomenon exists during mode I rock fracture. The variance and autocorrelation coefficient of AE counts grow significantly prior to rock fracture, and thus, the significant growth of variance and autocorrelation coefficient of AE signals can act as the precursory indicator of rock fracture. Compared to the autocorrelation coefficient, the precursors determined by the variance are more remarkable. The time interval between the precursory indicator using the critical slowing down theory and fracture moment ranges from 2% to 15% of the entire loading time. The findings in this study could facilitate better understandings on the rock fracture process and early-warning technique for rock fracture-related geological disasters.

中文翻译：

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通过临界减速分析确定脆性岩石I型断裂的前兆指标

与岩石有关的突然危险，例如滑坡，岩石破裂和坍塌，严重威胁了工程工作的安全性和使用寿命。关于突然断裂之前的关键过渡的前兆信息在岩石力学和工程中具有重要意义。这项研究调查了脆性岩石I型断裂过程中声发射（AE）信号和前兆指标的临界减速特征。利用破裂的人字形缺口巴西圆盘（CCNBD）标本，并伴有声发射监测。介绍了临界减速的原理以研究AE计数序列，并分析了方差和自相关系数与加载时间的关系曲线。结果表明，Ⅰ型岩石破裂过程中存在严重的减速现象。AE计数的方差和自相关系数在岩石破裂之前显着增长，因此，AE信号的方差和自相关系数的显着增长可以作为岩石破裂的先兆指标。与自相关系数相比，由方差确定的前体更为显着。使用临界减速理论的前兆指示器与断裂力矩之间的时间间隔为整个加载时间的2％至15％。这项研究的发现可以帮助人们更好地了解与岩石破裂有关的地质灾害的岩石破裂过程和预警技术。声发射信号方差和自相关系数的显着增长可以作为岩石破裂的先兆指标。与自相关系数相比，由方差确定的前体更为显着。使用临界减速理论的前兆指示器与断裂力矩之间的时间间隔为整个加载时间的2％至15％。这项研究的发现可以帮助人们更好地了解与岩石破裂有关的地质灾害的岩石破裂过程和预警技术。声发射信号方差和自相关系数的显着增长可以作为岩石破裂的先兆指标。与自相关系数相比，由方差确定的前体更为显着。使用临界减速理论的前兆指示器与断裂力矩之间的时间间隔为整个加载时间的2％至15％。这项研究的发现可以帮助人们更好地了解与岩石破裂有关的地质灾害的岩石破裂过程和预警技术。使用临界减速理论的前兆指示器与断裂力矩之间的时间间隔为整个加载时间的2％至15％。这项研究的发现可以帮助人们更好地了解岩石破裂过程和岩石破裂相关地质灾害的预警技术。使用临界减速理论的前兆指示器与断裂力矩之间的时间间隔为整个加载时间的2％至15％。这项研究的发现可以帮助人们更好地了解岩石破裂过程和岩石破裂相关地质灾害的预警技术。