Aggregates Manager

March 2017

Aggregates Manager Digital Magazine

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by Anthony Konya SPECIAL REPORT Six Sigma Six Sigma Six Sigma Drilling Blasting Drilling Blasting Blasting and A common problem for engineers and consultants for aggregates mines is the critical challenge of achieving proper blasting. Many of the problems faced came from operational ineffi ciencies in the drilling and blasting program. Most mines believe that better blast design will help save costs, improve fragmenta- tion, and decrease vibration, and, while this is all true, none of this can be achieved if the design cannot be achieved with reasonable accuracy. By achieving this accuracy, before implementing better blast designs and processes, most mines save upwards of 15 to 30 percent on their blasting costs. There are many ways to achieve accuracy, such as designing for inaccuracies, automating jobs, and blasting management. Designing for inaccuracies How does one design for inaccuracies in blasting? This is a common question when inaccuracies are fi rst encountered, because engineering out these inaccuracies is one of the easiest options with the least capital cost. However, this approach is extremely costly in the hidden costs of drilling and blasting. One of the fi rst people to study drill deviation on a large scale was Langefors. Langefors documented his extensive results from dozens of mines in his book The Modern Tech- nique of Rock Blasting and discussed ways to 'engineer out' drilling ineffi ciencies. He did this by analyzing the average errors in drilling from: • Collaring location – the drill setting up in the wrong place, causing the hole to begin in the wrong location; and • Alignment inaccuracies – this includes drilling improper an- gles and the deviation inside of the borehole when drilling. When Langefors studied a large multitude of blasts in Sweden, he concluded that, on average, improper collaring locations accounted for 4 inches of deviation, and alignment inaccuracies were approximately 0.04 inches per foot in bench blasting. To most, this may seem insignifi cant, but this is almost ±6 inches on a 40-foot bench. This means that between two holes the spacing may be reduced by 1 foot and the burden increased by 0.5 feet. A steady management approach to drilling and blasting can help operators lower their costs and achieve better fragmentation. 12 AGGREGATES MANAGER / March 2017

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