To investigate the effect of fracture distribution on the mechanical responses and failure forms of coal–rock combined masses under impact loading, dynamic impact tests on coal–rock-like combined bodies containing pre-existing cracks were carried out using split Hopkinson pressure bar. The dynamic mechanical properties and the failure and fractal characteristics of specimens under different impact velocities were investigated. The obtained results showed that the strength of fractured combined bodies was influenced by the positions and angles of cracks. It was found that fractures in coal sections had great influence on specimen strength and the maximum influence was obtained for the angle of 30°. An obvious strain rate effect was also observed on the dynamic strength of RCB (combined body with fractures in rock section) specimens. Fractal dimensions of the coal sections of cracked combined bodies were close to those of intact ones when at angles 60° and 90°, while they were smaller at angle 30°. The existence of cracks changed stress concentration in specimens under impact loading, changing their dynamic mechanics and failure characteristics, where fractures in coal sections with lower strength had a greater effect on the overall stability of combined bodies. Therefore, strengthening supporting work on the weak part of combined or layered rock masses has to be conducted in engineering practice and the failure of rock masses due to crack propagation in adjacent rock masses should be prevented.

中文翻译：

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裂合霍普金森压力杆试验中煤-岩样组合体破裂的动态力学性能和碎片分形特征

为了研究在冲击载荷下裂缝分布对煤岩组合质量体的力学响应和破坏形式的影响，使用霍普金森分压棒对包含预先存在的裂缝的煤岩样组合体进行了动态冲击试验。研究了不同冲击速度下试样的动态力学性能以及破坏和分形特征。所得结果表明，断裂组合体的强度受裂纹位置和角度的影响。发现煤断面的断裂对试件强度有很大的影响，并且在30°角时获得最大的影响。在RCB（岩石断面结合体）试样的动强度上也观察到了明显的应变率效应。角度为60°和90°时，裂化组合体的煤段的分形维数接近完整煤层的分形维数，而角度为30°时，它们的分形维数较小。裂纹的存在改变了试样在冲击载荷下的应力集中，改变了其动态力学和破坏特性，其中强度较低的煤段的断裂对组合体的整体稳定性影响更大。因此，在工程实践中必须加强对组合或分层岩体薄弱部分的支护工作，并应防止由于裂纹在相邻岩体中传播而导致岩体破坏。裂纹的存在改变了试样在冲击载荷下的应力集中，改变了其动态力学和破坏特性，其中强度较低的煤段的断裂对组合体的整体稳定性影响更大。因此，在工程实践中必须加强对组合或分层岩体薄弱部分的支护工作，并应防止由于裂纹在相邻岩体中传播而导致岩体破坏。裂纹的存在改变了试样在冲击载荷下的应力集中，改变了试样的动态力学和破坏特性，其中强度较低的煤段的断裂对组合体的整体稳定性影响更大。因此，在工程实践中必须加强对组合或分层岩体薄弱部分的支护工作，并应防止由于裂纹在相邻岩体中传播而导致岩体破坏。