Influence of stress and geology on the most prone time of rockburst in drilling and blasting tunnel: 25 tunnel cases

Rockburst exhibits different occurrence time characteristics during drilling and blasting in tunnel excavation, posing challenges to the safe and efficient construction of tunnels. In this study, 25 tunnels with rockburst hazards were examined. By employing the clustering method, we analyzed the characteristics of the most prone time (MPT) for rockburst. Furthermore, we investigated the contribution degree and influence mechanism of stress and geological factors related to the MPT of rockburst. The outcomes revealed that distinct tunnels exhibit diverse rockburst-prone times, leading to varying hazards and losses. The higher the maximum principal stress and the angle between it and the tunnel axis, the earlier the rockburst occurs. Moreover, the MPT of rockburst is influenced by both lithological types, macro and micro rock structures. When the joint intersects with the maximum principal stress at a small angle, rockburst occurs earlier. The stress direction, UCS, attitude of the dominant joint, and stress magnitude stand out as the principal controlling factors. The findings of this research can serve as a basis for assessing the MPT of tunnel rockburst, timing rockburst risk control measures, and selecting appropriate mitigation strategies.