Patent ID: 7707939
Filing Date: 2010-05-04
Classification: F42D

Abstract:
1. A method of blasting rock in a blastfield to cause fragmentation of the rock without excessive ground vibrations, the method comprising the steps of: providing two or more rows of blastholes in the rock, wherein the blastholes in at least one of said rows is arranged in two or more groups, each group comprising from 2 to 7 blastholes each of which is adjacent to another of said blastholes within the group; loading each blasthole with an explosive charge; providing blast initiation means associated with each explosive charge; and inducing timed actuation of each explosive charge via the associated blast initiation means to propagate stressfields from each blasthole; wherein the explosive charges in adjacent blastholes within each group of blastholes are actuated within 5 ms of one another, whereby the stressfields from the blastholes within each group combine prior to dissipation to enhance fragmentation of the rock, and wherein for each of said groups of blastholes a delay of at least 8 ms occurs between completion of actuation of explosive charges in the group and commencement of actuation of explosive charges in all others of said groups of blastholes, whereby the combined stressfields that propagate from blastholes within any group of blastholes at least substantially dissipate prior to actuation of explosive charges within blastholes of the other groups of blastholes.