Weakending of Taconite in Small Scale Explosive Tests

Abstract

The primary objectives in blasting taconite are to produce broken rock that permits optimum digging and shovel loading rates with minimum secondary breakage and eliminates primary crusher delays. Since at least 1990, much of the blasting research by explosives companies, academics, and mining companies has been directed toward determining the downstream benefits of increased blast energy, particularly on crushing and coarse grinding. Several papers have been published that attempt to quantify the cost benefits. However, so many variables are involved that most benefits are only indicated or estimated. A report entitled "Effects of Blasting on Milling," by C. M. Lownds and D. A. Bocca of Viking Explosives & Supply, Inc., and K. Nielsen, Professor, Department of Geology and Mineral Resources Engineering, Norwegian University of Science and Technology, was presented at the 1997 Duluth, Minnesota, SME Annual Meeting. It describes a rather simple method of explosively loading taconite samples and of evaluating the explosive effects on grindability.1 " The small-scale explosive tests were conducted on taconite rock pieces collected from the back of a muckpile instead of on diamond drill core or sawed and drilled cubes, as described in previous work.2 · 3 The testwork described in the following report was proposed as a continuation of the tests on rock fragments to examine more extensively the effects of small-scale explosive tests on rock weakening.