垂直孔复合消能爆破技术及其在建基面开挖中的应用

Vertical borehole shock-reflection blasting technique and its application in foundation excavation

针对白鹤滩水电站坝基角砾熔岩和柱状节理玄武岩互层的地质条件,研发了一种建基面保护层垂直孔复合消能爆破技术。该技术通过在炮孔底部安装高波阻抗球形垫块和铺设松砂垫层形成复合消能结构,利用冲击波在高波阻抗垫座的反射和松沙垫层的缓冲作用降低爆破对建基面岩体的冲击影响。在白鹤滩水电站开展现场爆破试验用于验证该技术,试验结果表明,垂直孔复合消能爆破技术可有效降低坝基岩体的扰动,孔底起爆条件下振动降低率达40%以上,有利于建基面开挖过程中的振动控制;且该技术能有效控制孔底损伤,保护建基面岩体,获得与水平预裂或光面爆破平整度相当的建基面。复合消能爆破技术在白鹤滩坝基及水垫塘基础开挖中得到了大规模应用,获得了良好的建基面成型效果,加快了施工进度,获得了明显的经济效益。

In order to protect the breccia lava and the columnar jointed basalt of the Baihetan foundation,a bench blasting technique with shock-reflection structure arranged at the borehole was developed. The shock-reflection structure consists of spherical shock-reflection block with high sonic impedance and flexible cushion with low sonic impedance,the reflection of stress wave at the spherical shock-reflection block surface and the cushion effect of flexible cushion can reduce the impact of the vertical borehole blasting on the foundation rock mass. The field experiment results at Baihetan hydropower station indicate that the shock-reflection blasting technique can effectively reduce the disturbance of dam foundation rock mass,and the vibration reduction rate is over 40% under the bottom ignition condition,which is conducive to the vibration control in the excavation process. And the shock-reflection blasting technique can effectively control the blast-induced damage in foundation rock mass, protect the foundation rock mass,and get a smooth foundation surface as the pre-splitting blasting or the smooth blasting. According to the field experiment results,the vertical borehole shock-reflection blasting technique has been successfully applied to the excavation of the Baihetan dam foundation and the plunge pool foundation,It has achieved good foundation forming effect,speed up the construction progress,and achieved significant economic benefits.