| 摘要 |
<p>The method of fragmentation blasting includes the step of forming blast holes (16) through a blast area (10) and also void holes (17) spaced between blast holes. The blast holes are charged with explosive material but the void holes are left empty to form free faces internally of the blasting area. Thus, the void holes will, in association with an external free face retract and reflect energy waves as additional tensile forces to more fully fragment the stone. Prior to forming the blast holes and void holes the blast area is split on a plane at or adjacent to the floor bottom to induce an interface between before fragmentation blasting takes place. This is done by drilling holes (12) on a plane as close as possible to that of the quarry floor (11) and loading the holes with explosive. Pre-splitting of the back and side face or faces of the blast area (10) may also be done before fragmentation blasting takes place. This is done by drilling new vertical holes (14) and loading the holes with explosive. The blast holes are charged and detonated sequentially blasting in sequence the explosive material in individual blast holes is detonated in sequence preferably separate quantities of explosive material are provided in each blast hole to form at least two spaced decks and each deck is ignited separately. The sequential blasting of individual blast holes and of the decks in each blast hole is controlled by a combination of short delay detonators and a sequential blasting machine. As a result of the void holes, the fragments of stone are small enough to eliminate the need for primary crushers and machinery for transporting large initial fragments to a primary crusher.</p> |
