Engineering & Mining Journal

AUG 2018

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Page 38 of 107

AUGUST 2018 • E&MJ 37 BLASTING efit technically because scaled distance is not used in signature hole analysis. In addition to this, not only is the vibration's peak particle velocity (PPV) completely wrong from what it would be in a normally confined borehole, but the frequency and wave trace from these boreholes is also completely wrong. They will give some attempt at modeling and say that the maximum PPV from this blast should be under, for example, 8.91 in. per second. The blast is fired, and the actual result is 3.2 in. per second. This is not a signature hole analysis and does not provide any data to the mine, this will not stand up in court, and this provides no guarantees on any ground vibration, let alone gives any real timing or loading advice to the mine. Additionally, we have seen this pro- cess perverted even further with compa- nies using this as a method to run a linear regression or 95% confidence equation. These equations have been run since the USBM developed their original ground vibration prediction equations, yet they have never been run with this lack of un- derstanding of basic blasting principles. The goal of a linear regression is to de- termine, based on scaled distance, what the maximum PPV will be for a blast. These are always run with real blasting data from seismograph reports that are correlated to each blast that a mine runs. These models are then updated for each blast to form a new equation. This is crit- ical because each blast is functioning in the exact manner that the subsequent blasts (that will be predicted with the model) will function. The biggest important parameter in a linear-regression model is the understand- ing of confinement and at what point dif- ferent data sets need to be developed. One easy to understand example is production blasting and presplit blasting. In closer distances, presplit blasting will have a higher ground vibration than a production blast, for this reason they will not be mod- elled together but the data will be sepa- rated, and a separate linear-regression is developed, one for production and one for presplit blasting. Otherwise, the produc- tion blasting would be severally limited. A similar process is performed with different cardinal directions around a site (North versus South, for example). This is to help refine the linear-regression to not severely limit the amount of explosive a mine can put into a borehole. In recent years the au- thors and other industry experts have been developing methods to refine and increase the accuracy of these models. Current practices of firing completely confined holes in situations that are completely different from how the blast actually func- tions (such as dozens of feet behind the free face) and causes the science of linear regression to go backward, this extremely limits the mines loading procedures and should an exceedance of the limits occur give no technical background in court — oftentimes losing the case. In today's world, the mining environ- ment is very tough to navigate combining social, cultural and political aspects. In many cases, ground vibration from blast- ing can make or break a mine and exceed- ances of ground vibration limits can not only be costly, but cause mine shutdowns and mine managers and owners to face jail time. Mines should be able to trust the "subject-matter experts" that they bring in to help. It has been seen time and time again, however, that many of these "ex- perts" are more interested in selling more expensive products than giving a real solu- tion. The days of sales as technical work in the blasting industry need to be put to an end and replaced with good technical research and consulting. Calvin Konya is the founder of Precision Blasting Services (PBS) and Anthony Konya serves as project engineer for PBS. Surface Miner = Mining made easy. A WIRTGEN GROUP COMPANY 4200 SM: WIRTGEN Surface Miners cut, crush and load material in a single operation. WIRTGEN is the only manufacturer to cover a per formance spectrum of up to 3,000 tons per hour with direct loading by conveyor belt. This high output is based on high-performance cutting technology and a wealth of experience acquired in three decades of application technology. Take advantage of innovative solu tions from the technology leader. WIRTGEN GmbH · Reinhard-Wirtgen-Str. 2 . D-53578 Windhagen . T: +49 26 45 / 131 0 Surface Miner

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