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Acoustic emission and kinetic fracture theory for time-dependent breakage of granite

机译：用于花岗岩时间依赖性破损的声学发射和动力学裂缝理论

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Earthquakes, mine failures, and initiation of hydraulic fractures have all been associated with time-delayed breakage of rocks subjected to loads insufficient to incur instantaneous failure. To better model and identify failure precursors for rocks under these so-called static fatigue conditions, Acoustic Emission (AE) was monitored in beams of Coldspring Charcoal Granite subjected to constant three point loading. As a result of varying the magnitude of the loading, the times to failure range fromO(101)toO(105)seconds. The experiments show a number of consistencies in the AE data. In all cases the event rate exponentially declines for a period that is about 0.4–0.6 of the total time to failure. This period is followed by a period in which the event rate exponentially increases. The total number of events generated during these two periods is also consistent among the experiments. Motivated by these observations, we propose a modified kinetic fracture theory that captures both the period of event rate decline and the period of event rate increase. It does this by firstly accounting for early time depletion of available bonds for breakage, similar to previous models. The model also accounts for generation of critically stressed bonds in the vicinity of previous bond breakages due to stress redistribution, thereby also predicting the event rate increase and further providing consistency with the observed tendency of the events to become increasingly concentrated around the eventual plane of failure as time progresses.
机译：地震，矿井故障和液压骨折的启动都与经受载荷不足的岩石的岩石的时间延迟断裂有关。在这些所谓的静态疲劳条件下更好的模型和识别岩石的失效前体，在经受恒定三点载荷的冷尖炭花岗岩的梁中监测声发射（AE）。由于改变负载的幅度，失效范围的时间范围（101）也（105）秒。实验在AE数据中显示了许多常量。在所有情况下，事件率呈指数增长的次数下降约0.4-0.6的总时间才能失败。这一时期之后是事件率指数增加的时期。在这两个时段期间产生的事件总数在实验中也是一致的。通过这些观察结果，我们提出了一种改进的动力学裂缝理论，捕捉事件率下降和事件率增加的时期。它通过首先会计出于早期耗尽可用债券的破损，类似于以前的模型。该模型还考虑了由于应力再分布引起的先前债券断裂附近的批判性紧张键，从而预测事件率增加并进一步提供了与事件的观察到趋势的一致性，以越来越集中在最终失败平面周围。随着时间的推移。

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