GB778760A - Improvements in or relating to the blasting of ore, rock, overburden and the like - Google Patents

Abstract

778,760. Blasting rock and charges therefor. MAUMEE COLLIERIES CO. Jan. 16, 1956 [Jan. 26, 1955], No. 1456/56. Classes 9 (1) and 68 (1). To blast rock, instead of lowering waterproof bags nlled with ammonium nitrate explosive into a vertical shothole as in Specifications 767,860 and 776,810, a bag 7 of resilient, waterproof, plastic material such as polyethylene is lowered into the hole, the bag being long enough to line the hole, and granular ammonium nitrate is then poured into the bag. Furthermore primer cartridges, which may be as in Specification 776,108 are placed in the bag, so that no point in the blasting charge 6 is more than 4.6 to 10.7 ins. from a primer 4. A tamper 12 is used to ram charge 6 into the bag and so eliminate air spaces. To lower the bag into the hole, a weight 11 or a cartridge of granular explosive is placed in the bottom of the bag 7, the mouth of the bag being held in the open end of the hole 1 by a funnel which has a locating shoulder 10. The ammonium nitrate after being mixed with finely divided combustible material, e.g. carbon black, in a rotary mixer (not shown) descends through a spout 14 into the bag and flows around the tamper. A fuze cord 5 connected to the primer 4 may be replaced by a blasting cap. When sufficient explosive has been charged into the bag, stemming material is introduced. This material may be placed directly on top of the explosive or the bag may be wrapped around the fuze cord and the tamping poured on to the bag. In an alternative method for shot-holes, which are burned into the ore then enlarged by " springing", plastic bags containing the granular explosive are dropped at intervals into the bag 7, so that these bags spread and compress the explosive poured into the bag 7.