Method of loading blast hole with explosive

摘要

A technique is provided for loading an ammonium nitrate-fuel oil (ANFO) explosive mixture upwardly into a vertical blast hole extending as much as 70 feet or more from the open end at the face of the rock structure into which the blast hole is drilled. In order to achieve adequate packing in the hole the ANFO is maintained "soft" by keeping the ammonium nitrate particles substantially free of anti-caking materials. First the hole surface is moistened with water. If the surface dries before the hole is completely loaded, the remaining unloaded length is again moistened. The particles of explosive are blown into the hole through a hose as a mixture with air at a velocity sufficient to bring about packing and sticking of the ANFO in the blast hole. The packing is sufficient to keep the ANFO from falling out of an upwardly extending blast hole. The top end of the hose is centered in the blast hole near the top end of the hole and the stream of air and soft ANFO impacts on the closed end of the hole and packs the explosive to a density of about 0.8 gm/cc. The hose is gradually retracted from the hole as it is filled. Preferably the hose is maintained reasonably straight at all times so that it can be pushed up a long blast hole without kinking. A special centralizer is used at the end of the hose in the hole to help break up ANFO particles.