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

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.

Automated summary

This study investigates the effects of axial static stress and confining pressure on the dynamic compressive behaviors of granite. It introduces a new index called Confining Pressure Increase Factor (CPIF) to evaluate the strength enhancement induced by confining pressure. The study also highlights the importance of the Energy Storage Limit (ESL) in the energy absorption and release process, and how it varies in different situations.