In deep rock engineering, evaluating the likelihood of rock burst is imperative to ensure safety. This study proposes a new metric, the post-peak dissipated energy index, which accounts for strain rate and size effects in assessment of the rock burst proneness of a rock mass. To investigate rock burst proneness, conventional compression tests were conducted on limestone and slate samples with different length to diameter (L/D) ratios (ranging from 0.3 to 1.5) at four different strain rates (0.005, 0.01, 0.5, and 1.0 s−1). Based on the testing observations, the actual rock burst proneness was classified into three categories (no risk, low risk, and high risk). A new criterion was also established using the post-peak dissipated energy index, which is the ratio of elastic energy to total dissipated energy. The impact of the strain rate and L/D ratio on rock burst proneness was analyzed. The results indicated that increased strain rates cause a strong hardening effect, leading to staged growth of rock burst proneness. However, the rock burst proneness decreases non-linearly with the increasing L/D ratio. The accuracy of the proposed criterion was validated by comparison with existing criteria, demonstrating that the energy-based index ensures a reliable evaluation of the rock burst proneness of a rock mass. The proposed method has excellent potential for practical application in deep rock engineering.
Anisotropy affects the mechanical behaviours of rock, especially for application in rock engineering. In this study, a digital drilling method is proposed to evaluate the mechanical anisotropy of rock. In consideration with the critical friction, the cutting efficiency and contact stress are determined from the revised drilling model to characterize the drilling process. For six types of rock, a series of drilling tests are conducted on three axial directions using the coring bit. The anisotropy of rock strength is obtained from the point load test to compare with the anisotropy of drilling characteristics. Correspondingly, an anisotropy criterion is established. A critical point is identified in the evolution of contact stress and the plot of drilling parameters, corresponding to the critical friction. Result indicates that the evolution of contact stress with inclination angle suggests the similar elastic and plastic stages (inclination angles of 5 and 12, respectively). The typical evolution is also confirmed by the critical depth of the friction point. Moreover, the cutting efficiency and contact stress at the critical point show the evident anisotropic characteristic. A comparison of
A
1
and
A
2
is conducted to determine the anisotropy index of drilling characteristics. Contact stress present the anisotropy sequence as shale (22.45) > gneiss (14.21) > schist 302 (10.74) and blue sandstone (10.07) > granite (7.29) > red sandstone (5.09). The consistency examination with strength anisotropy index suggests that the contact stress has a fitting correlation with an accuracy of 91 %. In summary, the digital drilling-based method provides a reliable evaluation for rock anisotropy, showing potential in practical application.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.