A multiple deck burn round for shaft sinking
- Ensign Bickford Co., Birchwood, WI (United States)
This paper describes an unusual design for a 12 foot diameter, 30 foot deep circular shaft shot in a close in urban environment less than 100 feet from occupied structures. It uses diagrams, video footage, and vibration results to describe a 3 deck, 17 hole burn round used to pull 17 feet in one lift. The round required a design that would shoot 20 pre-split holes and 17 production holes with 3 decks in each hole, and have them all armed before the first pre-split hole detonated. A relatively new 9/700 EZDET(R) detonator was used to prime each charge. Most production hole decks were loaded with Nitropel, a high velocity, high energy prilled TNT explosive. Accurate powder and stemming gauges were fabricated and used to insure positive control of charge loading height and weight. The round design used a charge weight which yielded a Scaled Distance of as low as 38. Also, the present state of the art in cap accuracy would indicate a serious overlap potential in many of the 62 charges in the shot. However, the shot resulted in low vibration, excellent fragmentation and depth of pull, and no complaints from the scores of very close neighbors.
- OSTI ID:
- 433682
- Report Number(s):
- CONF-940144--
- Country of Publication:
- United States
- Language:
- English
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