Microstructural investigation of subcritical crack propagation and Fracture Process Zone (FPZ) by the reduction of rock fracture toughness under cyclic loading
Microstructural investigation of subcritical crack propagation and Fracture Process Zone (FPZ) by the reduction of rock fracture toughness under cyclic loading
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DOI：
10.1016/j.enggeo.2016.04.035
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发表时间：
2016-06-24
影响因子：
7.4
通讯作者：
Erarslan, Nazife
中科院分区：
文献类型：
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作者：
Erarslan, Nazife
本研究介绍了在布里斯班凝灰岩盘试件上进行的实验室直径压缩试验的结果，以进一步了解亚临界裂纹扩展的微观力学和微观结构动力学。通过研究静载荷和循环载荷对岩石i型（拉伸）断裂韧性（K-IC）的响应，研究了无腐蚀化学环境下岩石在机械载荷作用下的强度变化。在某些情况下，与静态情况相比，裂纹可以在较低的负载水平下生长。这种现象被称为亚临界裂纹扩展，它取决于断裂过程区（FPZ）的行为。发现循环荷载下的K-IC响应在极限荷载和字形裂缝前损伤机制方面与静荷载下的K-IC响应不同。在最高幅值增加循环加载试验中，静态K-IC最大降低43%。对楔形缺口裂纹尖端表面进行了详细的扫描电子显微镜（SEM）检查，发现两种加载方式都会导致盘状岩石试样的疲劳。与静破坏试样相比，与循环加载试样的主要区别在于循环加载下颗粒破坏形成晶间裂纹，而静加载下沿解理面形成光滑明亮的裂纹。本研究认为，岩石的结构特征，如互锁和胶结颗粒、水泥体积、水泥矿物学等，对岩石的损伤行为以及FPZ和亚临界裂缝的发展起着非常重要的作用。(C) 2016 Elsevier B.V.版权所有
This study presents the results of laboratory diametrical compression tests performed on Brisbane tuff disc specimens to develop much-needed understanding of the micro-mechanical and micro-structural dynamics of sub critical crack propagation. The strength variation in rocks under mechanical loading without corrosive chemical environment was investigated by investigating the mode-I (tensile) fracture toughness (K-IC) response to static and cyclic loading. In some cases, cracks can grow at a lower load level compared to the static case. This phenomenon is called subcritical crack propagation and depends on,the behaviour of the Fracture Process Zone (FPZ). The K-IC response to cyclic loading was found to be different from that under static loading in terms of the ultimate load and the damage mechanisms in front of the chevron crack. A maximum reduction of the static K-IC of 43% was obtained for the highest amplitude increasing cyclic loading test. Detailed Scanning Electron Microscope (SEM) examinations were performed on the surfaces of the tips of the chevron notch cracks, revealing that both loading methods cause fatigue in the disc rock specimens. When compared with static rupture, the main difference with the cyclically loaded specimens was that intergranular cracks were formed due to particle failure under cyclic loading, while smooth and bright cracks along cleavage planes were formed under static loading. It is believed in this study that the rock texture characteristics such as interlocked and cemented grains, cement volume, cement mineralogy play very important role on damage behaviour of rocks and development of FPZ and subcritical cracking. (C) 2016 Elsevier B.V. All rights reserved.