Best practices: Drilling and blasting

By |  December 7, 2015

Cemex Balcones Quarry blast in New Braunfels, TexasLarry Mirabelli, senior manager at Buckley Powder Co., teamed with Bill Hissem, senior mining engineer at Sandvik Construction, to deliver a presentation on drilling and blasting at the 2015 Quarry Academy hosted by Dyno Nobel and Sandvik.

Mirabelli, who has more than 40 years of experience in explosives technology between Buckley Powder and Dyno Nobel discussed a concept with Hissem called “chemical crushing,” which the two describe as making drilling and blasting a symbiotic process to achieve better results. Pit & Quarry recently connected with Mirabelli to discuss this concept further, as well as best blasting practices.

P&Q: What are some of the most common blasting mistakes you see made at quarries?

Mirabelli: I feel the biggest mistake is separating drilling from blasting. The traditional method of drilling and blasting is to treat the two items as separate processes. A driller comes in to drill a hole; a blasting company puts explosives in the hole and blasts it. If you keep these two items separate, you cannot always achieve the best results.

It’s not “chemical crushing,” as [Hissem] and I call it. We really think quarries should manage these two activities as one. When these two are managed separately, you are likely to get non-uniform rock fragmentation. If you combine the processes, you can achieve a more uniform gradation that will make the crushing process easier down the production line.

Larry Mirabelli of Buckley Powder Co.

Larry Mirabelli, Buckley Powder

P&Q: Are quarries embracing the concept of fusing drilling and blasting?

Mirabelli: Some are embracing it. When we present this topic at Quarry Academy events, many of those attendees take this information back to their companies and have been successful at integrating it. They have told us they see rewards. We did a chemical crushing case study in 2009 at Capital Quarries in Jefferson City, Mo., to show the importance of tying drilling and blasting together for better results in the blast and reduced overall operating costs.

P&Q: Aside from the issue of separating drilling from blasting, are there any other issues related to blasting that should be addressed at quarries?

Mirabelli: Another big shortfall I see a lot is implementation of the blast pattern to the bench. Often, quarries will adjust their blast design to the bench condition. For consistency in results, it should really be the other way so that a straighter quarry face results after each blast. So instead of that approach, design and prepare the bench to accommodate your blast design. This will help maintain a straight face and improve the overall consistency of the blast pattern.

P&Q: A number of blasting jobs are contracted out. Is there anything quarries should focus on doing before a blasting company comes in?

Mirabelli: They should set quality standards that both the drilling and blasting contractors are expected to meet. If they are doing their own drilling or blasting, these quality standards should be met one in the same. Drill holes need to be placed at their proper position on the bench – top and bottom of the hole – to proper depth in an overall condition that will allow explosives to be loaded into them, and with all details documented in a drill log for communication to the blasting contractor. Blasting contractors should lay out the drill pattern based on a surveyed profile of the face. At a minimum, a profile survey should be done after drilling and before loading so that the proper explosive load can be determined for each blast hole based on the survey and drill log. A best practice would be to profile both before and after drilling. The post drilling survey will indicate how well the blast design was implemented. Measurement before and after each blast will lead to improved blast performance.


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