RESEARCH ON KEY TECHNIQUE OF ROCK ANCHOR BEAM EXCAVATION

Rock anchor beam,the sustentation structure of the bridge-type lift,is the emphases and difficulty in excavation of underground powerhouse.The underground powerhouse of Pubugou power-station was located in a high geo-stress area,which is characterized by complicated rock cracks and joints.Because of the high requirement of construction quality of rock anchor beam excavation and strict time limit for the project,some new blasting techniques were adopted.The'Controlled Blasting with Three-stage Ignition'was first used in central cutting excavation,and the'Vertical-slope Hole Controlled Blasting'was used in upside protective layer excavating of rock anchor beam.These new technologies reduced the blasting vibration and insured the construction quality of rock anchor beam excavation,creating the new records of blasting excavation in terms of 100% of leftover ratio of bore holes,0.2～0.8m of influencing depth caused by blasting and excavating,and only 8.7cm of the average rock face unevenness.