Multilevel cyclic loading–unloading uniaxial compressive testing combined with real‐time acoustic emission monitoring (AE) and post‐test computed tomography (CT) scanning was employed to investigate the anisotropic cracking propagation and the type of crack classification for interbedded marble. An AE parameter method using RA (ratio of rise time to amplitude) and AF (ratio of AE counts to duration) is used to classify cracking event modes and propagation characteristics. Results show that the fatigue strength and lifetime first decreases and then increases with increasing interbed orientation, and they reach a minimum for rock with an interbed orientation of 30°. In addition, the distribution of RA values and AF values is strongly influenced by the rock structure, especially the interbeds. Moreover, CT imaging reveals the difference between the cracking mode and it is found that the cracking propagation pattern is structurally dependent. An increase of RA value provides an early warning for rock failure.

中文翻译：

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多级循环单轴压缩载荷作用下夹层大理石疲劳裂纹扩展的实验研究

多层循环加载-卸载单轴压缩测试与实时声发射监测（AE）和测试后计算机断层扫描（CT）扫描相结合，用于研究夹层大理石的各向异性裂纹扩展和裂纹分类类型。使用RA（上升时间与幅度之比）和AF（AE计数与持续时间之比）的AE参数方法可对裂化事件模式和传播特性进行分类。结果表明，随着层间取向的增加，疲劳强度和寿命首先降低，然后增加，而层间取向为30°的岩石的疲劳强度和寿命达到最小值。另外，RA值和AF值的分布受岩石结构（尤其是夹层）的强烈影响。而且，CT成像揭示了裂纹模式之间的差异，并且发现裂纹扩展模式在结构上是相关的。RA值的增加为岩石破坏提供了预警。