Dynamic crack initiation in holed and jointed rock masses: A maximum energy release rate criterion and parametric influences

Focusing on the dynamic fracture characteristics of rock masses containing holes and joints, this study investigates the influence of joint geometric parameters on the crack initiation angle based on the maximum energy release rate theory. Dynamic impact tests using a split Hopkinson pressure bar (SHPB) were conducted to analyze the effects of joint length variations on energy conversion and crack initiation characteristics. A crack initiation criterion for rock masses with intermittent joints was established. The results indicate that high impact pressure enhances the hindering effect of joints on energy propagation, making the reinforcement effect of joint expansion on interface energy reflection more significant. The increase in joint dip angle leads to an initial increase followed by a decrease in the crack initiation angle, while an increase in hole diameter reduces the crack initiation angle. An increase in joint length promotes a larger crack initiation angle, and this effect becomes more pronounced at larger joint dip angles. A high friction coefficient suppresses shear expansion, increasing the difference in crack initiation angles at smaller joint dip angles and reducing the difference at larger dip angles. Additionally, under high strain rate conditions, the crack initiation angle is primarily controlled by the joint dip angle, and the differences in crack initiation angles among joints with varying dip angles diminish. When considering joint width, the crack initiation angle exhibits periodic fluctuations with changes in dip angle, and the influence of T-stress makes the crack initiation angle less sensitive to variations in joint length. The findings contribute to a deeper understanding of the dynamic failure mechanisms of rock masses with intermittent joints and provide theoretical support for related engineering practices. In this study, we establish a novel crack initiation criterion for rock masses containing holes and intermittent joints, grounded in the maximum energy release rate theory. We utilize split Hopkinson pressure bar (SHPB) tests to systematically vary joint dip angle, length, and aperture, alongside loading intensity and friction coefficient. Our key findings demonstrate: • Energy propagation and dissipation: High impact pressures significantly intensify joint obstruction and amplify interface energy reflection, while longer joints create more intricate dissipation pathways. • Geometry effects on crack angle: Joint dip angle initially increases then decreases the crack initiation angle, peaking near 45°, whereas larger apertures uniformly diminish the angle. Joint length markedly amplifies the angle at larger dip angles, and elevated friction suppresses shear‐driven initiation. • Strain‐rate independence: Under high strain rates, the crack initiation angle is governed predominantly by joint dip angle, emerging as a critical state independent of loading duration. • Influence of T-stress and width: Incorporating joint width induces periodic fluctuations in initiation angle, and T-stress reduces sensitivity to joint length, particularly within mid-range dip angles. • These results unravel the dynamic failure mechanisms inherent in naturally fractured rock masses, delivering both a rigorously validated initiation criterion and actionable insights for geotechnical design under dynamic loading scenarios (e.g., blast, seismic). We believe our findings will hold broad interest for rock mechanics researchers and engineers focused on slope stability, tunneling, and impact‐related geotechnical hazards.