Istanbul Technical University, Geological Engineering, Istanbul, Turkey.
Konya Technical University, Geological Engineering, Konya, Turkey.
PLoS One. 2022 Nov 3;17(11):e0276214. doi: 10.1371/journal.pone.0276214. eCollection 2022.
Micromechanical cracking processes in rocks directly control macro mechanical responses under compressive stresses. Understanding these micro-scale observations has paramount importance in predicting macro-field problems encountered in rock engineering. Here, our study aims to investigate the development of precursory damage zones resulting from microcracking pertinent to macro-scale rock failure. A series of laboratory tests and three-dimensional (3D) numerical experiments are conducted on andesite samples to reveal the characteristics of damage zones in the form of strain fields. Our results from discrete element methodology (DEM) predict that the crack damage threshold (σcd) values are 61.50% and 67.44% of relevant peak stress under two different confining stresses (σ3 = 0.1 MPa and σ3 = 2 MPa), respectively. Our work evaluates the strain fields within the range of the σcd to the peak stress through discrete analysis for both confining stresses. We note that the representative strain field zones of failure are not observed as soon as the σcd is reached. Such localized zones develop approximately 88% of peak stress levels although the confinement value changes the precursory strain localization that appears at similar stress levels. Our results also show that the distinct strain field patterns developed prior to failure control the final size of the macro-damage zone as well as their orientation with respect to the loading direction (e.g 17° and 39°) at the post-failure stage. These findings help to account for many important aspects of precursory strain field analysis in rock mechanics where the damage was rarely quantified subtly.
岩石中的微机械破裂过程直接控制着受压应力下的宏观力学响应。理解这些微观尺度的观察结果对于预测岩石工程中遇到的宏观场问题至关重要。在这里，我们的研究旨在研究与宏观尺度岩石破坏相关的微破裂引起的前兆损伤带的发展。对安山岩样品进行了一系列实验室试验和三维（3D）数值试验，以揭示应变场形式的损伤带特征。我们从离散元法（DEM）的结果预测，在两种不同围压（σ3 = 0.1 MPa 和 σ3 = 2 MPa）下，裂纹损伤阈值（σcd）值分别为相关峰值应力的 61.50%和 67.44%。我们通过对两种围压进行离散分析，评估了σcd 到峰值应力范围内的应变场。我们注意到，一旦达到σcd，就不会立即观察到代表破坏的应变场区域。尽管围压改变了在相似应力水平下出现的前兆应变局部化，但这种局部化区域大约在达到峰值应力的 88%时发展。我们的结果还表明，破坏前发展的明显应变场模式控制着宏观损伤带的最终尺寸及其相对于加载方向的方向（例如 17°和 39°）在破坏后阶段。这些发现有助于解释岩石力学中前兆应变场分析的许多重要方面，在这些方面，损伤很少被微妙地量化。
