Abstract This study reports the coefficients of the crack tip asymptotic field for the semi-circular bend (SCB) specimen made of anisotropic rocks when subjected to pure mode I loading. The finite element over-deterministic method is employed to determine the singular and higher order terms of the crack tip asymptotic field for a wide range of geometry and anisotropy parameters associated with the Mode I SCB test. These parameters are helpful when analysing the fracture path and failure mechanism of anisotropic rocks in cases where the process zone is large compared to the crack length. We also apply an energy-based criterion on the crack tip fields to evaluate the size of the K-dominant region as a function of geometry configuration and anisotropy. It is concluded that the ISRM-suggested size requirement for the SCB samples of rock can yield underestimated values of fracture toughness due to the constraints applied to the FPZ development.

中文翻译：

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各向异性半圆弯曲试样的裂纹尖端渐近场和 K 优势区

摘要 本研究报告了由各向异性岩石制成的半圆弯曲 (SCB) 试样在受到纯 I 型载荷时裂纹尖端渐近场的系数。对于与模式 I SCB 测试相关的各种几何形状和各向异性参数，采用有限元过确定性方法来确定裂纹尖端渐近场的奇异项和高阶项。在过程区与裂纹长度相比较大的情况下，这些参数有助于分析各向异性岩石的断裂路径和破坏机制。我们还在裂纹尖端场上应用基于能量的标准来评估 K 主导区域的大小作为几何配置和各向异性的函数。