Vertical borehole shock-reflection blasting technique and its application in foundation excavation
LU Wenbo1，2，HU Haoran1，2，YAN Peng1，2，CHEN Yong3，RONG Yaojiu4，WANG Zhilin4
(1. State Key Laboratory of Water Resources and Hydropower Engineering Science，Wuhan University，Wuhan，Hubei 430072，China；2. Key Laboratory of Rock Mechanics in Hydraulic Structural Engineering，Ministry of Education，Wuhan University，Wuhan，Hubei 430072，China；3. Sinohydro Engineering Bureau No. 8，Co.，Ltd.，Changsha，Hunan 410004，China；4. Baihetan Construction Department of China Three Gorges Construction Management Co.，Ltd.，Ningnan，Sichuan 615400，China)
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 cushioncan 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.
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2018, Vol. 37 
