Abstract The predictability of the failure process of underground rock mass located adjacent to a cavity is a key challenge in engineering practices. Therefore, the spallation failure of prefabricated elliptical holes in different orientations under various impact pressures was studied and analyzed by Hopkinson pressure bar. The failure process of long rod red sandstone was recorded in real-time by a high-speed camera during the experiment. The experimental results indicated that spallation did not necessarily occur in all the prefabricated holes, while the impact pressure had a great influence on the spall location of a defective rock mass. Also, the prefabricated holes located closer to the free surface experienced less damage under the impact of lower pressure than the holes located farther away from the surface. In addition, a finite element software, LS-DYNA, was employed to carry out equal-scale modeling and analysis of the circumferential stress variations in elliptical holes. The simulation results showed that the amplitude and wavelength of the stress wave would greatly affect the damage of elliptical defective holes and the initial defects weakened the integrity of the rock. Furthermore, the results showed that the larger the amplitude and wavelength, the lower the stress concentration coefficient of the rock in tensile failure and the most significant damage around the hole was observed at the peak tensile stress.

中文翻译：

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砂岩中不同瞬态入射波对预制椭圆孔的剥落损伤机理

摘要 邻近空洞的地下岩体破坏过程的可预测性是工程实践中的一个关键挑战。为此，采用霍普金森压杆对不同方向的预制椭圆孔在不同冲击压力下的剥落破坏进行了研究和分析。实验过程中通过高速摄像机实时记录了长杆红砂岩的破坏过程。试验结果表明，并非所有预制孔都发生剥落，而冲击压力对缺陷岩体的剥落位置影响很大。此外，靠近自由表面的预制孔在较低压力的影响下比远离表面的孔受到的损坏更小。此外，使用有限元软件 LS-DYNA 对椭圆孔中的周向应力变化进行等比例建模和分析。模拟结果表明，应力波的幅值和波长对椭圆缺陷孔的破坏影响很大，初始缺陷削弱了岩石的完整性。此外，结果表明，振幅和波长越大，岩石在拉伸破坏中的应力集中系数越低，并且在峰值拉伸应力处观察到孔周围的破坏最显着。模拟结果表明，应力波的幅值和波长对椭圆缺陷孔的破坏影响很大，初始缺陷削弱了岩石的完整性。此外，结果表明，振幅和波长越大，岩石在拉伸破坏中的应力集中系数越低，并且在峰值拉伸应力处观察到孔周围的破坏最显着。模拟结果表明，应力波的幅值和波长对椭圆缺陷孔的破坏影响很大，初始缺陷削弱了岩石的完整性。此外，结果表明，振幅和波长越大，岩石在拉伸破坏中的应力集中系数越低，并且在峰值拉伸应力处观察到孔周围的破坏最显着。