Abstract Weak bedding planes and joints predominate the anisotropic behaviours of rock mass under external static or dynamic loads. In this article, the rate-dependent fracture performance of a bedding plane-rich rock was experimentally investigated via a split Hopkinson pressure bar (SHPB) system. Based on the dynamic loading of notched semi-circular bending rock specimens at various intersection angles between the notch and bending planes (from 0° to 90°), a couple of outcomes were obtained. It is found that the deflection distance into the bedding plane linearly decreases with bedding angle, indicating the failure pattern of such stratified rock changes from bedding-dominated to rock matrix-dominated. With increasing the loading rate, the trajectory of the propagating crack converted from deflection along the bedding plane to direct penetration into the rock matrix. A factor, anisotropy index ηai, was used to determine the rate-dependent fracture toughness transition at various bedding angles. This anisotropy index exponentially decreases approaching the extreme isotropic value (ηai = 1) with loading rate. The mechanism of bedding plane-dominated rock fracture was analysed in terms of an energy criterion where the theory was verified by the experimental results. This article is helpful for the deep understanding of fracture behaviour in stratified and grain-based heterogeneous rock structures under dynamic loads.

中文翻译：

---

加载速率对弱层理面丰富岩石各向异性和裂纹扩展的影响

摘要 在外部静载荷或动载荷作用下，岩体的各向异性行为主要是弱层理面和节理。在本文中，通过分离式霍普金森压力棒 (SHPB) 系统对富层理面岩石的速率相关断裂性能进行了实验研究。基于缺口半圆形弯曲岩石试样在缺口和弯曲平面之间的各种交叉角度（从 0° 到 90°）的动态加载，获得了几个结果。发现进入层理平面的偏转距离随层理角度线性减小，表明这种层状岩石的破坏模式从以层理为主转变为以岩体为主。随着加载速度的增加，扩展裂缝的轨迹从沿层理平面的偏转转换为直接渗透到岩石基质中。一个因子，各向异性指数 ηai，用于确定不同层理角度下与速率相关的断裂韧性转变。该各向异性指数随着加载速率呈指数下降，接近极端各向同性值 (ηai = 1)。从能量准则的角度分析了层理面主导的岩石断裂机理，并通过实验结果验证了该理论。本文有助于深入理解层状和粒基非均质岩石结构在动力荷载作用下的断裂行为。该各向异性指数随着加载速率呈指数下降，接近极端各向同性值 (ηai = 1)。从能量准则的角度分析了层理面主导的岩石断裂机理，并通过实验结果验证了该理论。本文有助于深入理解层状和粒基非均质岩石结构在动力荷载作用下的断裂行为。该各向异性指数随着加载速率呈指数下降，接近极端各向同性值 (ηai = 1)。从能量准则的角度分析了层理面主导的岩石断裂机理，并通过实验结果验证了该理论。本文有助于深入理解层状和粒基非均质岩石结构在动力荷载作用下的断裂行为。