锦屏二级水电站引水隧洞围岩岩爆特性研究

Rockburst Features of the Surrounding Rock in Jinping Second-stage Hydropower Station's Diversion Tunnel

为了解锦屏二级水电站引水隧洞围岩岩爆特性,对该工程区典型岩爆岩样系统地开展了岩石力学特性试验研究。试验结果表明:岩样较完整坚硬、抗压强度高,主要以脆性破坏形式为主;典型地层试样的岩爆倾向性指数平均值Wet均大于2.0,当地处高应力区时,岩爆特征明显;岩样卸围压破坏过程中变形特征规律为初始卸载围压越大,岩石的扩容效应越显著,与常规三轴压缩试验相比,岩样卸荷破坏的峰后应力跌落时的轴向应变变化较小,初始围压越大脆性破坏特征越明显;CT扫描断面与图像重组手段分析表明,试样在卸荷试验过程中,首先经历压密阶段,然后进入扩容状态直至破坏,破坏后存在"密度回弹"现象。卸围压试验中,试样瞬间发生破坏,多数伴有破裂响声,多数产生"双剪"破坏;利用岩体基本质量指标来描述岩石坚硬程度和岩体完整程度,提出了一种新的岩爆判据形式与分级标准,利用试验成果对提出的岩爆判据与分级进行了验证,结论与锦屏二级水电站辅助洞岩爆实际情况相符。

Rock mechanics tests were conducted on typical rockburst specimens to investigate the rockburst features in the diversion tunnel of Jinping second-stage hydropower station.Test results show that the rock samples are com-plete and hard of high compression strength,with brittle failure as the main failure mode.The rockburst proneness indexes （Wet ）of typical strata are larger than 2.0,and rockburst feature is obvious in high geostress area.In the unloading process,the dilatancy of rock specimens is more obvious when the initial unloading confining pressure gets higher.The axial strain of rock specimens when stress falls after peak changes less than that by conventional triaxial tests,and the brittle failure is more obvious when confining pressure gets higher.CT scanning and image re-formation results suggest that during the unloading,the rock specimens experience the stage of compaction,state of dilatancy until failure,and then stage of density springback after failure.During the unloading test,failure happens instantly mostly with sounds and double shear damage.Hence the new rockburst criterion and classification stand-ard are proposed using the basic quality indicators of rock mass to describe the hardness and integrity degree of rock.The rock mechanics test results verified the criterion and classification which agree well with the rockburst properties in Jinping second-stage hydropower station.