Abstract

A series of triaxial repetitive impact tests were conducted on a 50-mm-diameter split Hopkinson pressure bar testing device to reveal the characteristics of dynamic stress–strain of sandstone under confining pressure, and the confining pressure in this study was set as 5 and 10 MPa. The results showed that sandstone is very sensitive to confining pressure and strain rate. As the confining pressure and strain rate increases, the dynamic strength, critical strain and absorbed energy also increases, however with the increases in number of impacts, they decrease. With impact numbers increases, the stress–strain curve of sandstone gradually transits from a Class I to a Class II. The dynamic statistical damage constitutive model used in the paper can describe the dynamic response of sandstone under confining pressure with repetitive impact. Various influencing factors, such as material characteristics, confining pressure, strain rate and damage on the dynamic mechanical behavior of sandstone are also fully considered in the model. The damage curve changes from concave to convex as the \({F \mathord{\left/ {\vphantom {F {F_{0} }}} \right. \kern-\nulldelimiterspace} {F_{0} }}\) increase. When the \({F \mathord{\left/ {\vphantom {F {F_{0} }}} \right. \kern-\nulldelimiterspace} {F_{0} }}\) exceed 0.5, the damage curve appears convex, and the damage is obvious. By comparing with the variation of the reflected wave waveform with the impact numbers, it is found that damage evolution law of the rock under confining pressure with the impact numbers is similar to that of the reflected wave waveform with the impact numbers, can reflect the damage degree of the rock specimen without other auxiliary equipment, which has been verified.

Article Highlights

• The stress-strain curve of sandstone under confining pressure with repeated impact changes from Class I to Class II, and it will become less obvious as the confining pressure increases.

• The constitutive model used in the article can well describe the dynamic mechanical properties, strain rate effect and its turning point of rock under confining pressure with repeated impact.

• The damage curve changes from concave to convex, and the damage evolution law is similar to that of the reflected wave waveform with the impact numbers.

中文翻译：

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围压下砂岩应力应变关系的反复影响

摘要

在直径为50mm的霍普金森分体式压力棒测试设备上进行了一系列三轴重复冲击试验，以揭示在围压下砂岩的动应力-应变特性，本研究中的围压设为5和10 MPa。结果表明，砂岩对围压和应变速率非常敏感。随着围压和应变率的增加，动态强度，临界应变和吸收能也增加，但是随着冲击次数的增加，它们减小。随着冲击次数的增加，砂岩的应力-应变曲线逐渐从I级过渡到II级。本文所使用的动态统计损伤本构模型可以描述砂岩在围压下具有重复冲击的动力响应。该模型还充分考虑了各种影响因素，例如材料特性，围压，应变率以及对砂岩动态力学性能的破坏。损伤曲线从凹形变为凸形，因为\（{F \ mathord {\ left / {\ vphantom {F {F_ {0}}}} \ right。\ kern- \ nulldelimiterspace} {F_ {0}}} \）增加。当\（{F \ mathord {\ left / {\ vphantom {F {F_ {0}}}} \ right。\ kern- \ nulldelimiterspace} {F_ {0}}} \}超过0.5时，会出现损坏曲线凸起，且损伤明显。通过与反射波波形随冲击次数的变化进行比较，发现冲击波在围压下岩石的损伤演化规律与冲击波在冲击波作用下的损伤演化规律相似，可以反映出损伤的发生。岩石标本的高度，无需其他辅助设备，已得到验证。

文章重点

• 围压下具有反复冲击的砂岩应力-应变曲线从Ⅰ类变化为Ⅱ类，随着围压的增大，应力-应变曲线将不明显。

• 本文所使用的本构模型可以很好地描述岩石在反复压力作用下的动态力学性能，应变速率效应及其转折点。

• 损伤曲线从凹面变为凸面，损伤演化规律与具有冲击次数的反射波波形相似。