Coupling effects of confining pressure and strain rate on rock compressive strength
Yongan Ma, Chong Yu, Haibo Li, Zun Cheng, Yaqun Liu, Jiajun Wu
Abstract
This study systematically investigated the coupling effects of confining pressure and strain rate on the dynamic strength of granite through dynamic triaxial compression tests. A dynamic strength criterion was developed to incorporate these coupling effects for further analysis. Moreover, the research thoroughly revealed the underlying mechanism by which these coupling effects influence the rock strength. The results revealed that both confining pressure and strain rate significantly enhanced the dynamic strength of rock; however, a mutual inhibition effect emerged under their coupling. Specifically, as the confining pressure increased, the strengthening effect of strain rate gradually diminished. Conversely, increasing the strain rate weakened the strengthening effect of confining pressure. The proposed strength criterion successfully predicted rock strength under various confining pressures (0-225 MPa) and strain rates (10 -6 -600 s -1 ). It achieved an average prediction error of only 8.3%, which represents a 65% improvement in accuracy compared to models that consider confining pressure and strain rate effects independently. At the micro-mechanism level, increasing confining pressure and strain rate promoted crack propagation in a transgranular (TG) mode, thereby enhancing the overall rock strength. However, under the coupling effects, the interference and interaction of TG cracks weakened the overall strengthening effect. This indicated that the competitive interaction between confining pressure and strain rate during crack propagation constitutes the intrinsic mechanism underlying their mutual inhibitory effect on rock strength. This study provides a more accurate theoretical basis for understanding the dynamic responses of rocks and contributes valuable insights for disaster prevention and control in deep rock engineering projects.