Rockbursts are one of the prominent problems faced by deep underground engineering. Not only do they affect the construction progress, but they also threaten the safety of construction personnel and equipment, and may even induce earthquakes. Therefore, the prediction of rockbursts has very important engineering significance for the excavation of deeply buried tunnels. In this paper, a new indicator for stability and optimization evaluation of hard, brittle surrounding rock under high geo-stresses, namely the minimum energy storage limit of surrounding rock induced by transient unloading, is proposed. In addition, the time for erecting support for tunnel excavation in the rockburst area and the impact of excavation dimensions on rockburst are investigated. The results show that transient unloading during the tunnel excavation process will reduce the energy storage limit of the rock mass. When the strain energy density of the local surrounding rock exceeds the minimum energy storage limit of the rock mass, the rock mass energy is suddenly released, and rockburst occurs. Rockburst is most likely to occur at 0.42–0.65 D away from the working face. The increasing length of a round adopted in high geo-stress areas will make the surrounding rock unstable and increase the probability of rockburst.
As a unique geological hazard in a high-geo-stress environment, rockburst happens with strong suddenness, randomness, and destructiveness, but the mechanism of its occurrence in a deep-buried tunnel in a high-geo-stress environment needs further study. Based on the analyses of the stress field of the rockburst section of Ping’an Tunnel, which is over-long and deep-buried, the occurrence mechanism of rockburst is figured out. Furtherly, the intensity and location of rockburst are predicted by using the rockburst criterion. Results show that there exists large compressive stress at the side wall of the tunnel, which is the main cause of rockburst. Under a high-geo-stress condition, due to the existence of unfavorable factors like structural planes, high intensity rockburst is likely to happen in the middle of the tunnel face after the sudden release of original rock stress. Arranging stress-releasing holes in the rockburst section can effectively reduce the possibility of rockburst by releasing the original rock stress in advance. The research results can deepen the understanding of the mechanism of rockburst in a high-geo-stress environment and provide scientific basis for the prevention and control of rockburst in similar engineering projects.
As the main source of pressure around tunnel rock masses, in-situ stress must be thoroughly understood to accurately predict the potential for rockburst events, especially in high-stress construction environments. Yet, theoretical advancements in this field remain behind practical engineering demands. In this study, we used a multiple linear regression approach to determine the initial in-situ stress field across the entire Ping’an tunnel and employed strength theory to predict rockburst occurrence. The regression results closely match field measurements, and the consistently low p-values confirm the reliability of the model. In addition, the rockburst intensity predicted based on the strength criterion shows strong agreement with real-world engineering observations, demonstrating the rationality of the proposed methodology. The findings from this research contributes to a deeper understanding of the initial in-situ stress field in rockburst-prone tunnels under high in-situ stress conditions and provide a scientific basis for tunnel alignment optimization and rockburst risk assessment. These insights hold significant practical implications for the construction of similar projects.