Blasting: The story of breaking rock

By |  September 11, 2020
Photo: koer/iStock / Getty Images Plus/Getty Images

As we increase the data and methods, the future of blasting will incorporate artificial intelligence programs to monitor large amounts of data received from drills, explosives, initiation systems, drones, cameras, LIDAR/photogrammetry and the instrumentation of the future. Photo: koer/iStock / Getty Images Plus/Getty Images

In this final article of the Blasting Through the Ages series, we close the story of blasting and end by asking key questions: What does the future of this industry hold? What are the next steps in the onward progression, and who will be the ones to pick up the torch and carry us forward?

To this point, we have taken a dive into the history and the future of drilling, explosives and initiation systems – and there is much to be excited about.

New drilling technologies will pave the way for automatic fleet management, and operator-less drills will be at most sites around the world. The explosives of the future will be powerful and green, allowing us to break more rock with less fumes. And the initiation systems of the future will be wireless and allow for remote loading of holes, improving safety and blasting efficiency.

Now, we shall head once more into the breach to talk about blast design: Where have we come from, and where do we venture next?

The ancient era

Once again, we will revisit that day in 1627 when the first blast was fired. This time, though, we can seek no answers from the ancient texts of blasting, as the method of design was never disclosed or published. 

No blast reports exist that can back-calculate the methods of blasting and the design completed. In this story, our hero is not the blast designer, but the Hungarian Mining Tribunal. 

At the time, Hungary was competing for investments to continue to lead Europe as the top mining economy, and the tribunal was tasked with ensuring that mines were operating properly and safely. 

After witnessing the blast, the tribunal knew other mines in the area would have to adopt this blasting technology for Hungary to take the lead on mining in Europe. Early records indicate that the Hungarian Mining Tribunal developed powder factor – the first blast design system – which was noted at the time to be a crude, rough way to estimate how many pounds of explosive were needed to break a certain tonnage (or volume) of rock.

This is an important point to understand. Powder factor was one of the first blast design technologies. At the time, it was not considered a good design method, but one that could get blasting started at a project. 

The blasters and engineers later took over and modified powder factor to work better as they collected data. This was the only design approach until the 1870s, when the blasting world changed with the widespread adoption of dynamite.

With dynamite’s adoption, the old methods of powder factor no longer worked. The early blast designers’ theories from the early 1800s then began to take hold. These theories were modified to work with dynamite, giving decent results to start a project and relying on field modifications to optimize. 

Photo: ArtEvent ET/iStock / Getty Images Plus/Getty Images

Could future refinements in blast design bring the elimination of oversize material?
Photo: ArtEvent ET/iStock / Getty Images Plus/Getty Images

In the mid-1890s, the first full-scale theory of blast design was developed and called shear theory. This new theory worked from rock breakage principles to design blasts and became the prominent blast design of the early 1900s. Shear theory, while now understood to be wrong in many cases, was one of the early theories about how a bench broke and designing the “line of resistance,” which, today, is called the burden. 

Ancient blasting ends with the worldwide stage using explosives, a fall of powder factor and the development of shear theory.

The age of militarization

Blasting’s next age is heavily influenced by the beginning of explosives use in the military. 

The history of commercial blasting and military applications of explosives is intertwined due to the world wars. At this time, many explosives engineers worked with military organizations across the world. While some academics did not directly transfer into the military, almost all work transferred to military applications of explosives because the major research funding was toward weapons rather than mining.

It is critical to understand that in the universities of the day – and, in many cases, today – professors had to research what was being funded. The large military funding led to many new discoveries, particularly in shockwave physics.

Following the discovery of the nuclear bomb, almost all research in explosives shifted to shockwaves. This led C.W. Livingston to begin working on shockwaves in rock blasting. Although his work did not demonstrate shockwaves fully, it led others to begin investigating further.

Other researchers looked at shockwaves in similar methods as Livingston. These researchers all included in their work that shockwaves, at maximum, could only account for up to 50 percent of the fragmentation of the rock – a point that was often missed in training and short articles. 

Still, as studies went on, major errors were found in the methodology. These include points such as:

■ The shockwave doesn’t truly form from commercial explosives.

■ The bench doesn’t break when the shockwave hits, but over 10 times after the shockwave is gone.

■ The shockwave theories never could 

be practically designed with, on any level.

■ Packaged explosives produce no shockwave in the rock.

■ A powder factor of more than 8 pounds per cu. yd. would be required to see any signs of shockwave breakage.

The shockwave theory was great for the military, but it does not apply to blasting. Shockwaves led to many great theories on blast design, none of which could ever be practically applied and, thus, powder factor design was brought back into existence. 

This was not because powder factor was a good design tool. In fact, researchers often discussed how it was an extremely poor design tool, but they turned to powder factor because it worked to get a project started – just like in the early days of the Hungarian Mining Tribunal.

Modern blast design

With the loss of good, practical design techniques, powder factor quickly became the frontrunner in blasting, with some modifications to account for proper burden from shear theory. 

To correct the lack of practical methods of design, Richard Ash set out to provide a new design approach. Ash’s approach began with shear theory and the modifications previous authors made through the years to account for independent variables.

Ash surveyed nearly 100 mining operations, blasting programs and the different design variables they each used. He found the averages for each borehole size, and determined that a person could multiply the borehole diameters, throughout a range of diameters, by a constant to calculate the burden, stemming and subdrill. This became the basis of independent variable design.

As the years passed, Ash brought on a new student, Calvin Konya, at the Missouri School of Mines. Together, they worked on blast design and the understanding of how blasts broke rock through gas pressure. 

The work led Konya to find the principle of stiffness ratio and how it affected the spacing of a blast. The work transformed blast design from powder factor to a truly independent system that blasters and engineers could easily apply. 

Throughout the years, Konya went on to discover new relationships in burden, spacing and timing, developing the full theory of Independent Konya Variable Design. This gave blasters the ability to consider the explosive, bench geometry, rock type, rock structure and product available to fully design a blast that would function well. Minor modifications could then be made to optimize.

The future of blasting

Today, the blasting industry has a good blast design method in Independent Variable Design, and it functions in setting up a good blast and then making modifications to optimize on a site-specific basis.

The challenge often becomes: What is the best a site can expect to get? In my consulting work, I often come across sites that think they have achieved the best blasting possible, but they’re amazed by how much further they could have gone after dramatic improvements.

For this reason, the recent research development Precision Blasting Services has been undertaking is that of Multivariate Blast Design. This new design methodology allows us to take into account not just the optimal burden and stemming, but instead maps the relationships between these variables, enabling us to develop a truly optimal approach. Methods like N-Factor blast design provide the required experimental research to go into the process.

So how does this design methodology work? To start, the mine either has a blasting process that is already being used, or an Independent Variable Design is set. Certain goals are set in a special order to ensure not only great results, but also reliability in the system to produce consistent results. The variables are then mapped and tested, with multiple test sections within a single blast. 

This data is collected with the new systems that are available today, and the relationships are assigned. The new blast is then designed, and the data is collected to optimize the process.  A smaller site can go through this process in a few days, and larger sites typically take two to three weeks. 

The results thus far have been astonishing – for example, a 10-times improvement in fragmentation; not 10 percent, but 10 times less oversize. Another project went from having flyrock, which typically traveled 1,000 to 3,000 ft., to having no flyrock and blasting next to a sensitive structure. 

While the blast design is still improving with every new case study, the results are promising and appear to be the design methodology of the future.

As we increase the data and methods, the future of blasting will incorporate artificial intelligence (AI) programs to monitor large amounts of data received from drills, explosives, initiation systems, drones, cameras, LIDAR/photogrammetry and the instrumentation of the future. That will lead to a system of computers collecting and analyzing data, and likely designing the blasts using the Multivariable Design Principles. 

The drill and explosive-loading system will then get the blast ready and clear and scant the area to ensure no one is present. Utilizing AI programs such as deep learning technology, each new blast will collect critical data to refine and improve the next – leading to true optimization of blasting. 

The future of blasting is terrifyingly beautiful, with great innovations to come by blasters, engineers and managers who look to lead into a new age. They’re always pushing limits and never settling for “good enough.”

About this series

The Blasting Through the Ages series is an initiative by Pit & Quarry and Academy Blasting to tell the story of the blasting world. Throughout the ages, great blasters and engineers revolutionized blasting to the science and art we use today. This series will detail the historic methods of drilling, loading and blasting, as well as take readers throughout history to touch on major developments through the ages. The series includes four articles spanning four issues of the magazine, including:

Part 1. A Brief History of Drilling
Part 2. Explosive Advancement Through the Ages
Part 3. The Evolution of Initiation Systems
Part 4. Blasting: The Story of Breaking Rock

Anthony J. Konya is the 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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