A METHOD OF BLASTING IN MINES AND MEANS FOR CARRYING THIS METHOD INTO EFFECT

摘要

The process is used in mine galleries, shafts, quarries and public works and consists in arranging ordinary explosive charges in a single shot hole, at intervals along its length. The charges, which are separated from each other by effective tamping elements, are exploded successively fromt he top downwards. The shot hole has a relatively small diameter and the first conventional charge is introduced into the bottom of the hole, this is followed by the tamping elements and a second charge is then introduced followed by tamping elements and further charges. The detonating fuse is placed in position while the hole is filled and its special characteristic is that retarding elements are placed at intervals in the common sheath so that the charges are exploded in succession when the fuse is ignited outside the bore hole. On ignition a series of craters is formed which link up to give a cylindrical hole with a diameter ten times that of the initial bore; the hole is free from any debris.