Method of blasting multiple layers or levels of rock

Abstract

A method of blasting plural layers of material in a blastfield that reduces the amount of mechanical excavation required to expose a lower layer of material. The method includes using rows of equally spaced blastholes that pass through all of the layers and additional intermediate rows of blastholes that pass down only through the top layer. Each blasthole is capped with stemming material and includes one or more decks of explosive material and detonators, which air decks or inert stemming separating adjacent explosive decks. The detonators in layer are detonated first in order from row rearwards to throw a substantial amount of the blast material from the layer forwardly of free face onto the floor. In the same blasting cycle and within seconds of the throw blast, explosives materials in layers are detonated in a stand-up blast in which material in layers are broken up but otherwise are minimally displace or thrown forwardly.