Overcoming Oversize: Oversize and spacing (Part 3)
Additional improvements
The spacing of the blast is a complex variable relying on a number of factors, including the millisecond delay time between boreholes, the rock geology, the burden, the bench height and a variety of other complex blast design ratios.
The methods described in this article are extremely beneficial to get within the appropriate spacing, assuming that none of the other blast variables are changed. Using these methods can greatly reduce the oversize at a given site.
Still, these methods are not necessarily the best solution to minimize oversize and costs. For example, you may determine based on a 25-millisecond delay between boreholes that a spacing of 1.23 times the burden reduces the oversize of the blast by 10 percent. With today’s electronic delays, more flexibility can be built into the system and it may be determined that at a specific site, a 19-millisecond delay could be utilized with a spacing of 1.27 times the burden to reduce oversize by 13 percent.
In this case, the oversize would be reduced along with the overall drilling and blasting costs.
When analyzing a full site, multiple changes can dramatically improve performance and decrease costs. The process, though, is a complex one requiring the utilization of a multivariate blast design approach that is applied after the other processes covered in this article are completed.
Anthony Konya is vice president at Precision Blasting Services, consulting around the world in rock blasting and vibration from blasting. He is also the founder and CEO of Academy Blasting, an explosive engineering education company, and the host of AcademyBlasting.TV podcast.
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