Under certain extreme conditions in rock engineering works, fast change in temperature in the load-bearing rocks can happen. Known as thermal shock (TS), such process involves rapid temperature rise or drop, which causes fracturing in the rock material and thus can pose as a threat to the stability of the rock structures. To investigate the influence of thermal shock caused by fast cooling on the mechanical property of rock, laboratory tests are performed on heated granite which are cooled with different methods, with the highest cooling rate reaching 167.4 °C/min. The dynamic loading tests are performed on the heated granite specimens utilizing the split Hopkinson pressure bar (SHPB) system. The test results show that the dynamic compressive strength drops with the increase in heating level or cooling rate. This pattern is explained by the nuclear magnetic resonance (NMR) test data that the pores inside the heated granite increase both in size and quantity as heating level or cooling rate rises. Damage patterns of the tested granite specimen fragments are analyzed based on the observation with scanning electron microscope (SEM), and the mechanisms of thermal shock in granite are also discussed.

中文翻译：

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热冲击对承受动态载荷的花岗岩力学性能的影响

在岩石工程工作中的某些极端条件下，承重岩石中的温度可能会快速变化。这种过程称为热冲击（TS），涉及到温度的快速升高或降低，这会引起岩石材料的破裂，从而可能对岩石结构的稳定性构成威胁。为了研究快速冷却引起的热冲击对岩石力学性能的影响，对用不同方法冷却的加热花岗岩进行了实验室测试，最高冷却速率达到167.4°C / min。利用分开的霍普金森压力棒（SHPB）系统对加热的花岗岩样品进行动态载荷测试。试验结果表明，随着加热水平或冷却速度的增加，动态抗压强度下降。核磁共振（NMR）测试数据解释了这种模式，即随着加热水平或冷却速率的提高，加热的花岗岩内部的孔的尺寸和数量均增加。在扫描电镜观察的基础上，分析了被测花岗岩试样碎片的破坏规律，探讨了花岗岩中热冲击的机理。