ENGINEERING PRACTICE OF OVER-BURDEN CHAMBER BLASTING
XIE Fei-hong~1, GUAN Hui-ping~1, YAO Chao-gui~2, XIE Ye~2, YANG Lu-qiang~2 (1. Lanzhou Jiaotong University,Lanzhou 730070,China; 2. Gansu Risheng Blasting Engineering Co.Ltd,Lanzhou 730030, China)
Because of improper construction management in chamber excavation,the axial direction of a chamber has a great dviation from the designed direction,causing that the burden of charged chamber is increased from designed 40m to measured 57m.The chamber blasting with a burden larger than 50m is very rare,thus there being no referable experience.In the light of undulating topography,the pilot tunnel and charged chamber are excavated in a great slope of +172‰(approximate to 10°).With a short working term,the over-burden chamber blasting is crowned with success through reasonable utilization of the shape of excavated chamber, adjustment of linear charge's structure,position and mass,as well as increase of the end charge and adoption of dumbbell-like charge structure.