白鹤滩坝址柱状节理玄武岩爆破损伤质点峰值振速安全阈值研究

Study on safety threshold of peak particle velocity about blasting damage of columnar jointed basalt rock mass in Baihetan Dam site

白鹤滩水电站坝址处柱状节理玄武岩分布广泛,节理裂隙发育,爆破损伤控制是白鹤滩坝基开挖中的技术难题之一。结合白鹤滩水电站坝基保护层开挖,开展水平预裂爆破、水平光面爆破和竖直孔复合消能爆破条件下的现场爆破试验,基于不同爆破方式下爆前爆后岩体声波速度的对比检测数据以及坝基岩体钻孔内预埋速度传感器的振动测试结果,建立坝基岩体损伤程度与质点峰值振速的对应关系,提出与声波速度降低率相关的质点峰值振速安全阈值。现场试验结果表明:质点峰值振速安全阈值是岩体的固有性质,不受爆破方式和爆破参数的影响;在声波速度降低率为5%,10%和15%的条件下,对应的柱状节理玄武岩爆破损伤质点峰值振速安全阈值可大致确定为50,65和90 cm/s。

The columnar jointed basalt at Baihetan Hydropower Station is widely distributed,with joints and cracks largely developed.In this case,the control of blasting damage has become one of the critical technical problems in the excavation of Baihetan dam foundation.Based on the excavation of protective layer of dam foundation at Baihetan Hydropower Station,we conducted in-situ blasting tests with horizontal presplitting blasting,horizontal smooth blasting and energy-relief blasting with vertical holes.By comparing the acoustic velocity of rock mass before and after each blasting tests,and the vibration test results from embedded velocity sensors in the rock mass of dam foundation,we established a relationship between the damage degree of rock mass and the peak particle velocity,and proposed a safety thresholds of peak particle velocity associated with the reduction rate of acoustic velocity.The test results showed that the safety threshold of particle peak velocity is the intrinsic property of rock mass,which is not affected by the blasting method and parameters.Under the condition of 5%,10%and 15%reduction rate of acoustic velocity,the corresponding safety threshold of peak particle velocity can be roughly determined to be 50 cm/s,65 cm/s and 90 cm/s.