Coal Age

MAR 2019

Coal Age Magazine - For more than 100 years, Coal Age has been the magazine that readers can trust for guidance and insight on this important industry.

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Page 30 of 51

March 2019 29 blasting continued best design approach available in the market today. It is also used by most major international powder companies for blast design and in their blast design software. If one assumes the spacing along the strike from the Konya Design is the baseline spacing, they can then determine how the spacing changes based on changes from the deposi- tional environment. From this it can be seen that when the burden is in- creased by 18% (to 118%) to account for bedding dipping into the cut, the correct modification to the spac- ing is to increase it to 116% of the burden for this scenario. However, the powder factor design does the opposite and reduces the spacing well below the baseline, which will lead to poor fragmentation and the generation of fines between bore- holes and large boulder in front of the face. When accounting for the depositional environment, powder factor design changes spacing in the opposite way that it should, which leads to extremely poor results. After the depositional environ- ment has been considered, the next factor to consider is the geolog- ic structure, which is primarily the jointing of the blast. With heavily jointed rock, the burden can often be extended by 30% to the original design burden. The proper way to ac- count for the spacing in this situation is to increase the spacing by 130%, however, with powder factor design, it would actually reduce the spacing to 83%. When using powder factor design, the only way to keep the pow- der factor equivalent is to shrink the spacing. This would have extremely poor performance due to the spac- ing being too close and causing a splitting action between boreholes. In most situations, the blaster would then reduce the burden to improve the fragmentation and expand the spacing back to the normal design not taking into account the structure. This would likely produce extremely fi ne material, much fi ner than what the mine needs and leads to a large increase in drill and blast costs. Figure 2—Changes to Hole-to-Hole Timing and its impact on Powder Factor Versus Stiffness Ratio. WIRTGEN GmbH · Reinhard-Wirtgen-Str. 2 . D-53578 Windhagen . T: +49 26 45 / 131 0 Highest daily output in soft rock in soft rock The new 220 SM 3.8 / 220 SMi 3.8: Tough machine for soft rock. Maximum cutting performance thanks to the 3.8 m wide cutting unit. This makes the WIRTGEN Surface Miner ideal for selective mining of raw materials in mines of all sizes. Low cost per tonne of extracted material and the fact that drilling and blasting are not required make the proven mining method even more economic and safe. Take advantage of innovative solutions from the technology leader. A WIRTGEN GROUP COMPANY Stand FS.1011

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