Effect of detonator position on fragmentation at Kevitsa open pit mine

Abstract. Blasting is one of the main operations in open pit mining and effective rock blasting can have a major impact on the overall economy of the mine. To obtain optimal rock fragmentation by blasting, explosive energy must be well-utilized, well-distributed, and targeted to the rock mass that we aim to fragment. A position of a detonator in a blasthole affects all of the above. The aim of this thesis was to study the effect of detonator position on fragmentation at the Kevitsa open pit mine. The theoretical optimum for the detonator position in the explosive column was defined and tested in practice. In addition, the effects on bench floor conditions were investigated. The practical study consisted of blasted test fields within production blasts, where the current blasting practice used in Kevitsa was compared to the test design representing the theoretical optimum. The effects were measured and studied with shovel-mounted machine vision cameras, test drillings, and loading machine operator feedback forms. Considering optimal fragmentation and less damage below the bench floor level, both theoretical and field studies indicated that the detonator position plays an important role in rock fragmentation, and that the detonator position in the middle of the explosive column allows for significant improvement in rock fragmentation and bench floor conditions. The results of this study can be applied more generally in open pit blasting