Analysis of the Suitability of Different Anchor Bolt Support Systems for Rockburst Mitigation and Optimization of Anchor Bolt Parameters
To evaluate the support effectiveness of active rockboltanchor bolt-based active support systems in rock-burst-prone tunnels,a case study was conducted based on the Jiulingshan Tunnel.The secondary stress on tunnel walls and rock strength were obtained using the stress relief method and point load test.A comparative analysis of the suitability of rockburst prediction criteria was carried out,along with inversion of the initial stress field of the tunnel.Based on these results,the rockburst suppression mitigation effects of active and passive support systems were compared from the perspectives of stress and energy.Additionally,the key parameters of active support sys-tems under varying different rockburst gradelevels were explored.The findings indicate the followingthat:(1)Com-pared to passive support,the active support system can significantly reduces the maximum value ofσθ/Rb around the tunnel the maximum stress around the tunnel and suppresses the intensity of rockburst intensityoccurrences.The"energy absorption and release"effect of the active support system is more pronounced,aligning better with the prin-ciples of rockburst mitigation;(2)Increasing rockbolt anchor bolt strength and decreasing rockanchor bolt spacing both can improve the performance of the active support systems in mitigating rockburst;(3)For medium and intense rockburst scenarios,enhancing rockbolt anchor bolt strength proves to be more effective and economical than reducing rockbolt anchor bolt spacing.
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