Engineering & Mining Journal

JUL 2019

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HAUL ROAD MANAGEMENT JULY 2019 • E&MJ 47 www.e-mj.com haul at 0% grade. Segment C is 3% gentle rise to the Run-of- Mine dump point. Starting with a fresh wearing course and traffic handling 125,000 tons per day (t/d) through 20 days, the rolling resis- tance grows (segment B) from 3% to 4%. "At this site, we evalu- ated this change in rolling resistance if we changed the sheeting material. In other words, if we improved the sheeting material, will it reduce the rolling resistance? What we found is that we could significantly reduce the rolling resistance over the first two-thirds of that operating cycle at least. "The percentage loss in speed (or increase in cycle times) is very steep over the first week or so of operation and then it flat- tens out," Thompson said. "By changing the sheeting, that rate of loss can be reduced. Haul road segment B, which is the flat road, is particularly sensitive to changes in rolling resistance." Looking at the average percentage cost increase for the un- improved conditions, the costs really escalate quickly over the first week of operations (red line in Figure 5). The other two roads are less sensitive to those cost increases. The orange arrow indicates when we should intervene in terms of road mainte- nance. "The yellow line shows a high cost is associated with daily road maintenance and drops to a minimum in four days and then starts to increase again," Thompson said. "What that is telling us is that we are spending too much money on mainte- nance, which we are not recouping in terms of reduced vehicle operating costs and increased productivity." With the changes in sheeting material selection and manage- ment, the mine can extend the maintenance frequency on those roads. We have extended it from every second day to every fourth day and almost weekly on segment C simply by changing the sheet- ing material and bringing it closer in line with the specifications equated with a lower rate of rolling resistance degradation over time and reaping the benefits associated with improved productivity. Looking at unimproved vs. the improved conditions (See Fig- ure 6), the top red line represents the amount of material we are able to move on a daily basis. It's reducing as the rolling resis- tance increases, but the rate of decrease has been significantly reduced through re-sheeting. Similarly, the blue line represents the amount of haulage that would have to be supplemented to maintain the 125,000-t/d target. "The supplementation kicks in a little bit later with those improved conditions," Thompson said. "Those will be the basis on which you can asses the val- ue-add for the road improvement campaign as far as ripping off the old sheeting material, relaying better wearing course or a full road re-construction is concerned." Safety must always be paramount in any improvement cam- paign, but as shown in this article, assessing the value-add is an important adjunct in the process. Returning the road's surface to close to original condition minimizes the rolling resistance and further deterioration. Proper haul road management also minimizes production losses due to increased cycle time and lower productivity. This article was adapted from a presentation Roger Thompson gave at Haulage & Loading 2019, which was held during March in Tucson, Arizona, USA. Formerly a professor for the University of Western Australia's Mining Engineering department, Thompson started his own consultancy geared toward haul road design and construction for mining operations (www.mininghaulroads.com) Zero DPM and significant heat reduction SUBSCRIBE NOW to receive product information and performance results at macleanengineering.com EV for UNDERGROUND MINING

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