雅鲁藏布江峡谷段盆因拉隧道岩爆预测

Rockburst Prediction of Penyinla Tunnel in Brahmaputra Valley Section

盆因拉隧道地处雅鲁藏布江峡谷段高地应力地区。为了保证施工安全,采用水压致裂法在盆因拉隧道内进行了地应力测量。基于测试数据,通过线性回归方法分析了围岩应力场分布特征,采用Russenes判据和侯发亮临界埋深判据分析了隧道中发生岩爆的临界深度,并对不同埋深段的岩爆趋势进行了预测。结果表明:隧址区最大水平主应力为24.7～27.4MPa,方位为近北东向35°,具有极高地应力水平,侧压系数平均值为1.7;隧道埋深在200m以下发生岩爆的可能性较小,但局部会有弱岩爆发生,200～400m埋深处有发生弱—中等岩爆的可能,大于400m埋深处有发生强烈岩爆的可能;发生岩爆的理论临界深度为325m,而实际发生岩爆的最小深度为300m。因此,在施工过程中应采取合理的开挖方式及必要的工程应对措施降低岩爆灾害的影响。

Penyinla tunnel is located in Brahmaputra valley section with high ground stress.In order to ensure construction safety,ground stress was measured in Penyinla tunnel by hydro-fracturing method;distribution characteristics of stress field of the surrounding rock were analyzed by linear regression method;the critical depth of tunnel rockburst was calculated by Russenes criterion and HOU Fa-liang critical depth criterion,and the rockburst tendency in different depths of section was predicted.The results showed that the maximum horizontal principal stress was 24.7-27.4MPa,the direction was about NE 35°,the ground stress was extremely high,and the average of lateral pressure coefficient was 1.7;the possibility of rockburst was low when the depth of tunnel was less than 200m,but weak rockburst happened partly,weak-medium rockburst happened possibly when the depth was 200-400m,and strong rockburst happened possibly when the depth was more than 400m;the theoretical critical depth of rockburst was 325m,but the actual minimum depth of rockburst was 300m.Therefore,reasonable excavation and necessary engineering measures should be adopted for the tunnel construction to avoid rockburst disaster.