Cracking processes affected by bedding planes in Opalinus shale with flaw pairs
Cracking processes affected by bedding planes in Opalinus shale with flaw pairs
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DOI：
10.1016/j.engfracmech.2017.03.003
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发表时间：
2017-05
影响因子：
5.4
通讯作者：
S. Morgan;H. Einstein
中科院分区：
文献类型：
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作者：
S. Morgan;H. Einstein
了解岩石的开裂过程对于基本材料行为和工程应用是重要的。在评估非常规油气储层和设计核废料处置库时，对页岩裂解过程进行表征和预测是必要的。特别令人感兴趣的是层理面对开裂过程的影响。出于这个原因，我们在这项研究中测试了一种这样的页岩，Opalinus页岩。对具有两个预先存在缺陷和不同层理平面方向的棱柱形试样进行了一系列无侧限压缩试验。采用高速和高分辨率图像捕捉裂纹萌生、扩展和裂纹对之间的聚并，研究层理面取向和裂纹对几何形状的影响。结果表明，当层理面垂直于最大施加压应力方向时，裂纹角和裂纹对桥接角对裂纹过程的影响与未设置层理面的岩石相似。然而，当层理面与最大压应力方向更加一致时，裂纹沿层理面传播的频率更高。这种视觉观察是独一无二的，因为以前的研究并没有实时描述顺层面（弱表面）的裂缝。因此，本研究的结果有助于理解各向异性岩石的裂缝。
Understanding the cracking processes of rock is important regarding the fundamental material behavior and in engineering applications. Characterizing and predicting the cracking processes in shale is necessary when assessing unconventional oil and gas reservoirs and designing nuclear waste repositories. Of particular interest is the effect of bedding planes on the cracking processes. For this reason we tested one such shale, Opalinus shale, in this study. A series of unconfined compression tests were conducted on prismatic specimens with two pre-existing flaws and various bedding plane orientations. High speed- and high resolution imagery were used to capture crack initiation, -propagation and -coalescence between the flaw pairs and study the effects of bedding plane orientation and flaw pair geometry. It was found that in specimens with bedding planes aligned perpendicularly to the maximum applied compressive stress, the effects of the flaw angle and flaw pair bridging angle on the cracking processes were similar to those observed in previously tested rocks without bedding planes. However, as the bedding planes became more aligned with the direction of the maximum compressive stress the cracks initiating at the flaw tips propagated more frequently along the bedding planes. This visual observation is unique as previous studies did not characterize, in real-time, cracking along bedding planes (weak surfaces). Hence, the results from this study contribute to the understanding of cracking in anisotropic rocks.