As one of the most crucial mechanical parameters of the rock materials, the effect of brittleness on the deformation and failure is of great practical significance for geotechnical construction and disaster prevention and mitigation. In this paper, the deformation and failure behaviors of the different brittle samples under dynamic loading were investigated using a split Hopkinson pressure bar (SHPB) experimental system. Besides, scanning electron microscopy (SEM) was also employed to study the relationship between the microscopic failures and rock brittleness and strain rate effects. The results revealed that the brittleness indexes BI₃ and BI₅ of the samples under uniaxial compression follow a linearly decreasing trend affected by the temperature changes, while the brittleness of the sample shows an increasing trend with the increase of strain rate under the dynamic loading. Also, the decline in the brittleness leads to an increase in the prepeak yield deformation phase of the sample under dynamic loading; after the peak point, the sample failure mode transitions from type I to type II with self-sustaining failure. Moreover, it was found that the dynamic strength increase factor presents a negative correlation with the sample brittleness. Finally, the macroscopic failure mode of the sample changes from split failure with multiple cracks to shear failure with few cracks due to the effect of decreasing brittleness. The failure surface of the sample gradually becomes smooth with the increase of brittleness, which manifests as a decrease in microcracks, and the gradual increase of the strain rate makes the failure surface rough, accompanied by an increase in microcracks.

中文翻译：

---

脆性对煤系砂岩动力力学行为影响的实验研究

脆性作为岩石材料最重要的力学参数之一，对变形和破坏的影响对岩土工程施工和防灾减灾具有重要的现实意义。在本文中，使用霍普金森分体式压力棒（SHPB）实验系统研究了不同脆性样品在动态载荷下的变形和破坏行为。此外，还利用扫描电子显微镜（SEM）研究了微观破坏与岩石脆性和应变率效应之间的关系。结果表明，脆性指数BI ₃和BI ₅在单轴压缩下，随着温度变化，样品的脆性随应变率的增加而呈线性下降的趋势，而随着动态载荷的增加，样品的脆性则呈增加的趋势。同样，脆性的下降导致在动态载荷下样品的峰前屈服变形阶段增加。在峰值点之后，样本失效模式会从I型转变为具有自我维持失效的II型。此外，发现动态强度增加因子与样品脆性呈负相关。最后，由于脆性降低的影响，样品的宏观破坏模式从具有多个裂纹的分裂破坏变为具有少量裂纹的剪切破坏。