Abstract To explore their dynamic fracturing behaviours and failure mechanisms, transversely isotropic phyllite rocks with five bedding plane angles were investigated for full-field strain Brazilian disc tests under different strain rates using a split Hopkinson pressure bar and high-speed digital image correlation (DIC) technology. Two kinds of crack evolution processes: the cracks in specimens with low bedding angles activated near the non-loading point, and other cracks initiated at the centre of the disc prior to exceeding the peak stress were observed. Considering the four types of failure modes characterized by different mechanisms, the dynamic failure mechanism of transversely isotropic rock was discussed. The Brazilian disc strength of transversely isotropic rock under subjected to impact loads was computed by introducing the patchy weakness model to reflect the dominant role of the rock matrix in the dynamic test. The DIC results demonstrated that additional random orientation defects are activated and the competition for evolving into cracks becomes intense, indicating that cracks develop less along bedding planes as the strain rate increases. Moreover, the fracture patterns of the transversely isotropic phyllite specimens changed under static and dynamic conditions. Therefore, it is necessary to study the properties of transversely isotropic rocks under dynamic impacts rather than simply using inferences from static results.

中文翻译：

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巴西圆盘试验对冲击载荷下各向异性千枚岩的全场变形测量

摘要 为了探索其动态破裂行为和破坏机制，使用分裂霍普金森压力棒和高速数字图像相关（DIC）研究了具有五个层理平面角的横向各向同性千枚岩在不同应变率下的全场应变巴西圆盘试验技术。观察到两种裂纹演化过程：在非加载点附近激活的低层理角试样中的裂纹，以及在超过峰值应力之前在圆盘中心开始的其他裂纹。考虑到具有不同机制特征的四种破坏模式，讨论了横向各向同性岩石的动力破坏机制。通过引入斑块弱点模型计算横向各向同性岩石在冲击载荷作用下的巴西圆盘强度，以反映岩石基体在动力试验中的主导作用。DIC 结果表明，额外的随机取向缺陷被激活，演化为裂纹的竞争变得激烈，表明随着应变速率的增加，沿层理平面的裂纹发展较少。此外，横向各向同性千枚岩试样的断裂模式在静态和动态条件下发生了变化。因此，有必要研究动态冲击下横向各向同性岩石的性质，而不是简单地使用静态结果的推论。DIC 结果表明，额外的随机取向缺陷被激活，演化为裂纹的竞争变得激烈，表明随着应变速率的增加，沿层理平面的裂纹发展较少。此外，横向各向同性千枚岩试样的断裂模式在静态和动态条件下发生了变化。因此，有必要研究动态冲击下横向各向同性岩石的性质，而不是简单地使用静态结果的推论。DIC 结果表明，额外的随机取向缺陷被激活，演化为裂纹的竞争变得激烈，表明随着应变速率的增加，沿层理平面的裂纹发展较少。此外，横向各向同性千枚岩试样的断裂模式在静态和动态条件下发生了变化。因此，有必要研究动态冲击下横向各向同性岩石的性质，而不是简单地使用静态结果的推论。