Effects of Stress Ratio and Stress Wave Frequency on Rock Crack Propagation and Damage Evolution during Rockburst

Rockburst is a dynamic instability phenomenon in deep underground engineering, fundamentally governed by crack initiation, propagation, and rapid energy release in highly stressed brittle rock masses. Understanding the coupled effects of stress conditions and dynamic disturbances on crack evolution is essential for improving rockburst prediction and mitigation. In this study, a fracture-mechanics-based numerical framework is developed to investigate the influence of stress ratio and stress wave frequency on crack propagation behavior and damage evolution during rockbursts. Controlled sinusoidal stress waves provide cyclic dynamic loading to systematically isolate frequency and stress-ratio effects. The numerical model incorporates cohesive-zone-based fracture behavior to capture crack initiation and unstable propagation, and its predictions are examined through laboratory-informed trend analysis and limited cross-lithology validation. Parametric simulations reveal that decreasing the stress ratio significantly accelerates the crack growth rate and promotes earlier instability, while increasing the stress wave frequency intensifies damage accumulation and fragmentation by enhancing dynamic crack interaction. Crack propagation transitions from stable extension to rapid coalescence as frequency increases, leading to more severe rockburst characteristics. Comparative analyses across different lithologies indicate consistent qualitative trends in crack propagation behavior, despite variations in material properties. Acoustic emission indicators and force-displacement responses further support the identified damage evolution stages. Due to limited specimen numbers, the results are interpreted in a trend-oriented and mechanismbased manner rather than through statistical inference.