白龙江引水工程六盘山隧洞地应力分析及岩爆风险评估OA

[Objective]Taking the deeply buried Liupanshan tunnel of the Bailong River Diversion Project as the research background,this study aims to systematically investigate the distribution characteristics of the in-situ stress field along the tunnel alignment and to assess the rockburst risk of hard-rock sections under high-stress conditions,thereby providing a scientific basis for early-stage project planning,construction safety control,and support design.[Methods]A comprehensive approach combining field testing,numerical simulation,and theoretical analysis was employed.(1)Geological survey and deep-borehole hydraulic fracturing tests were conducted to obtain measured in-situ stress data from representative boreholes along the tunnel alignment.(2)Based on the measured data,a three-dimensional geomechanical model was established,and a multivariate regression inversion method was used to invert the initial in-situ stress field of the entire study area.(3)By integrating the Russenes criterion,the Turchan-inov criterion,and the criterion of the ratio of chamber damage depth,a multi-criterion comprehensive evaluation of rockburst risk was conducted for the hard-rock sections.[Results](1)In-situ stress characteristics:Along the tunnel alignment,horizontal stress was dominant,and the maximum horizontal principal stress was mainly oriented in the NEE-EW direction,forming a small angle with the tunnel axis,which was favorable for surrounding rock sta-bility.The stress magnitude increased with depth and was significantly influenced by faults and valley topography,resulting in localized stress concentration and stress differentiation.(2)Inversion verification:A comparison be-tween the measured data and inversion results from the deepest borehole ZK2301 showed good agreement in the deep zone,verifying the reliability of the inversion model.(3)Rockburst risk:The multi-criterion assessment indi-cated that rockburst risk increased with burial depth along the tunnel alignment:no rockburst at depths ≤197 m;weak rockburst at depths of 197-344 m;moderate rockburst at depths of 344-629 m;and strong rockburst at depths＞629 m.Sections with strong rockburst risk accounted for a relatively large proportion of the entire tunnel,mainly concentrated in hard-rock zones with high burial depths.[Conclusion]The in-situ stress along the Liupans-han tunnel is generally at a moderate-to-high level,providing conditions conducive to rockburst occurrence.The se-lected tunnel axis orientation is reasonable and favorable for surrounding rock stability.However,strong rockburst risk exists in hard-rock sections with large burial depths.Therefore,it is recommended that appropriate rockburst monitoring and mitigation measures should be implemented for high-risk tunnel sections during construction.This study provides critical guidance for the safe construction of the project and offers valuable reference for rockburst prediction and prevention in similar deeply buried hard-rock tunnels.