Effects of axial static stress and confining pressure on the dynamic compressive behaviours of granite

Abstract

This study aims to investigate experimentally the effects of axial static stress and confining pressure on the dynamic compressive behaviours of granite. A new index of confining pressure increase factor (CPIF) was introduced to evaluate the confining pressure-induced strength enhancement, a modified definition was proposed to determine the dynamic deformation modulus, and the roles of energy storage limit (ESL) were highlighted to explain the energy absorption and release process. The results showed that when the axial static stress was less than a threshold value that was equivalent to the rock’s elastic limit, it coupled with the confining pressure and elicited positive effects on the strength enhancement of the rock. However, once the threshold value was exceeded, the axial static stress weakened the rock while the confining pressure began to strengthen the rock in a more significant way. Moreover, the dynamic deformation modulus increased as the static stresses increased (including axial static stress and confining pressure) when the rock remained in the linear elasticity under the static loading, while it declined when the rock suffered from damage before the impact. Furthermore, the results revealed that the ESL tended to play critical roles in the process of energy absorption and release in different situations.

Keywords:

• Granite
• dynamic compressive behaviour
• coupled static–dynamic loading
• axial static stress
• confining pressure

Acknowledgements

The authors wish to thank Professor Xibing Li and Associate Professor Fengqiang Gong at the Central South University (China) for their helps on the experimental apparatus.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research work is supported by the 973 Program of China [Grant number 2015CB057906]; the National Natural Science Foundation of China [Grant number 51409245].