Dealing Effectively With Cap Rock, Without Creating Excessive Flyrock and/or Airblast
(Room Concorde A)
30 Jan 16
3:45 PM
-
4:45 PM
Tracks:
Blasters Training Seminar
Dealing with cap rock to obtain adequate fragmentation in the collar zone, while controlling flyrock and airblast, is a common problem facing many blasting operators, particularly for close-in blasting. Decreasing the stemming has some benefits, but always increases the risk of getting uncontrolled flyrock and excessive airblast. Proven techniques have been developed with the use of stab holes to deal with minimizing oversize in the collar zone. However, many operators do not like the stab hole technique because it requires additional holes with more drilling, and the placement of stab holes in-between production holes could restrict vehicles from safely travelling on the blast site without running over the holes. An alternative technique which eliminates all of the problems associated with decreased stemmed and stab holes, is with the use of a stem charge. The stem charge is placed directly in the stemming column. The stem charge quantity, where it is strategically placed in the stemming column, and how it is delayed are all critical for its success. But when properly implemented, the stem charge technique has easily improved fragmentation in the collar zone from 5 to 10 fold with no adverse effects pertaining to flyrock and/or airblast. Example calculations, cratering theory and a few case histories will be thoroughly cover in this presentation.