Time-dependent cracking and brittle creep of rock is fundamental to understanding the long-term evolution and dynamic failure in underground rock engineering. In the present paper, we present a systematic laboratory investigation into the control of single open macrofractures of differing orientations on time-dependent cracking and brittle creep in sandstone using digital image correlation (DIC). For a given macrofracture inclination angle β, we find that the failure of macrofractured sandstone under a constant stress is accompanied by the generation of more tensile fractures (wing cracks and secondary cracks) than in our constant strain rate experiments. This result differs from experiments performed on intact sandstones, for which macroscopic failure under a constant stress and constant strain rate were essentially identical. The nucleation site for the wing cracks is β-dependent. As β is increased, the crack nucleation position gradually moves from the center of the fracture towards the fracture tip with a decreasing speed. The kink angle of the secondary crack (k₁) increases quasi-linearly with the increase of fracture angle γ. With the increase of the secondary crack angle θ, the kink angle of the tail crack (k₂) shows different increasing trends for the left-lateral and right-lateral shear. The secondary crack could be inclined at a maximum of 26° (θ) to the maximum principal stress direction. Creep bursts—transient accelerations in deformation—are more easily triggered in macrofractured rock than in initially intact rock, and coincide in time with the coalescence of secondary cracks. The likelihood of occurrence of a creep burst was found to be higher for lower values of β. Finally, we present a secondary crack location map that defines the swing interval and identifies the fracture mechanism. The influence of a macrofracture, and its orientation, on damage evolution and the likelihood of creep bursts during interseismic periods provides crucial information for those tasked with monitoring hazards associated with the dynamic failure of crustal rocks.

岩石的随时间变化的开裂和脆性蠕变是理解地下岩石工程中长期演化和动态破坏的基础。在本文中，我们使用数字图像相关 (DIC) 对砂岩中不同方向的单个开放宏观裂缝控制随时间变化的开裂和脆性蠕变进行了系统的实验室研究。对于给定的宏观裂缝倾角β，我们发现，与我们的恒定应变率实验相比，在恒定应力下宏观裂缝砂岩的破坏伴随着更多拉伸裂缝（翼状裂缝和二次裂缝）的产生。这一结果不同于对完整砂岩进行的实验，后者在恒定应力和恒定应变率下的宏观破坏基本相同。翼裂纹的成核位置是β依赖性的。随着β的增大，裂纹形核位置逐渐从断口中心向断口尖端移动，速度逐渐降低。二次裂纹的扭折角( k _{1 )随着断裂角}γ的增加呈准线性增加。随着二次裂纹夹角θ的增大，尾部裂纹扭结角( k ₂ )在左旋和右旋剪切下呈现出不同的增大趋势。二次裂纹最多可向最大主应力方向倾斜 26° ( θ )。蠕变爆发——变形的瞬态加速——在宏观裂缝的岩石中比在最初完整的岩石中更容易被触发，并且在时间上与次生裂纹的合并一致。对于较低的β值，发现发生蠕变爆裂的可能性较高. 最后，我们提出了一个二次裂纹位置图，它定义了摆动间隔并确定了断裂机制。宏观裂缝及其方向对震间期损伤演化和蠕变爆裂可能性的影响为那些负责监测与地壳岩石动态破坏相关的危险提供了重要信息。