Abstract To investigate the influence of weakly filled joint angles on the dynamic mechanical properties and fracture evolution mechanism of sandstone, dynamic uniaxial compression tests were performed on sandstone specimens with joint angles of 0°–90° under strain rates of 35–125 s−1 and an interval of 15° using a modified split Hopkinson pressure bar (SHPB) apparatus. The dynamic stress–strain relationship, dynamic strength, dynamic peak strain, energy characteristic, failure mode, typical failure progress, crack coalescence category, fracture micro-mechanism, and theoretical analysis were examined in this research. The test results indicated that both the dynamic compressive strength and peak strain of jointed sandstone first decreased and then increased with the increase in the joint angle. To maximise the energy reflection coefficient and minimise the absorbed energy density, a critical joint angle α (approximately 45°), was employed. The specimens with joint angles of 0°, 15°, and 30° exhibited considerable plastic deformation capacity, whereas the brittle failure feature of specimens with joint angles of 60°, 75°, and 90° was more typical than that of intact specimens. The stress bimodality phenomena of the specimen with a joint angle of 45° were more distinct than those of the specimen with a joint angle of 60°. Four types of crack coalescence behaviours were identified during the dynamic fracturing processes of the jointed specimens using a high-speed camera; subsequently, these were compared with the crack coalescence categories of jointed specimens under static loading. Moreover, the micro-fracture morphology well-revealed the macroscopic fracture behaviours of jointed sandstone specimens. It was further confirmed that the variable tendency of the dynamic compressive strength of jointed specimens based on experimental results agreed with the theoretical analysis.

中文翻译：

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深巷道不同角度弱充填节理砂岩动力力学特征及裂缝演化机制

摘要 为了研究弱填充节理角对砂岩动态力学性能和断裂演化机制的影响，对节理角为0°～90°的砂岩试件进行了动态单轴压缩试验，应变速率为35～125 s-1。和使用改进的分体式霍普金森压力棒 (SHPB) 装置的 15° 间隔。本研究对动态应力应变关系、动态强度、动态峰值应变、能量特性、破坏模式、典型破坏过程、裂纹合并类别、断裂微观机制和理论分析进行了研究。试验结果表明，节理砂岩的动态抗压强度和峰值应变均随着节理角度的增加而先减小后增大。为了最大化能量反射系数并最小化吸收的能量密度，采用了临界关节角α（大约45°）。接头角度为0°、15°和30°的试样表现出相当大的塑性变形能力，而接头角度为60°、75°和90°的试样的脆性破坏特征比完整试样更典型。接头角为45°的试样的应力双峰现象比接头角为60°的试样的应力双峰现象更明显。使用高速相机识别了接头试样动态破裂过程中的四种裂缝聚结行为；随后，将这些与静态载荷下连接试件的裂纹合并类别进行了比较。而且，微裂缝形态很好地揭示了节理砂岩试样的宏观断裂行为。进一步证实，基于实验结果的连接试件动态抗压强度的变化趋势与理论分析一致。