Shockwave executive director of business development Mason Trouchet likens the company's product, STEMGEL™, to "solid water".

"STEMGEL™ is a hydrogel that brings vastly improved stemming consistency and valuable environmental improvements compared to aggregate stemming," he said.

While there have been developments in the drill and blast space over the years, particularly in detonator technology and explosives, Shockwave has tackled "the missing link" - the often-overlooked stemming process.

Typically, miners stem a hole that's been drilled for explosives with aggregate or cuttings - filling the hole around the detonator cord with crushed rocks to cork or contain the blast gas energy. Aggregate however has no effect on control of the pressure wave energy which is key for effective rock fragmentation.

"Most engineered drill and blast elements - the drilling, the detonator control, the explosives - are consistent, but then you have this one outlier of aggregate rock at the top of the hole," Trouchet said.

"Our solution to that is STEMGEL™ - a hydrogel, which is more effective and consistent every single time."

Shockwave developed and took four years to patent its gel system for stemming, the STEMGEL™ itself plus the GELDRIVE™ unit, custom designed to deliver the STEMGEL™ quickly and efficiently.

Trouchet said people knew water was more effective than rock at containing blast pressure.

"The key difference is, we've come up with a method to use what we've termed a solid water or hydrogel and we can get it into the stemming space efficiently," he said. 

 "We've turned the whole concept upside down and on its head, because we are now using this gel to attenuate, or slow down, and reflect the blast energy."

Why remove aggregate?

Trouchet said there were many key reasons to move away from using aggregate as a stemming method.

The first was to better control the pressure wave and maximise the impact of its energy within the hole and surrounding rock, all with reliable consistency for every blast hole in the pattern.

Blast energy was usually lost upwards and outwards through aggregate because it offered the path of least resistance.

The second was to reduce the noise, dust and fly rock created by a blast.

Trouchet said the pressure wave, or energy being used to break the rock, behaved differently when it encountered STEMGEL™.

"When it hits the gel, it will attenuate and reflect most of its energy (>90%) in the first 200mm of the stemming," he said.

"Like waves breaking against a cliff - they start to move back out, meet another wave and increase their size as they return.

"We're now using the stemming process to increase the peak pressures, which causes greater rock fragmentation.

"So using gel in this one little spot on the top of hole means it's no longer the weakest link and is causing the right kind of damage underneath with oscillating pressure waves."

At the top of the hole, trials have shown STEMGEL™ greatly reduces the blast damage to collars, reduces fly rock, and in underground situations, reduces damage to the face.

"What gets ejected out of the hole is water vapour, and the consequence of that is much less noise and significantly less dust," Trouchet said.

Upside down and underground

Not only has Shockwave's innovation turned traditional thinking on its head, STEMGEL™ can also be used upside down or sideways in underground operations.

The gel can be pumped into vertical or horizontal holes and sets within seconds to hold in place, Trouchet explained.

He said Shockwave could also accommodate water in the hole by adjusting the STEMGEL™/water ratio.

Sleeping on the job

Another advantage to using STEMGEL™ is its ability to remain in place for a month, Trouchet said.

"Sometimes you'll load a shot with an intention to fire it the next day but for whatever reason, everything is delayed and it might take a week or two or even three," he said. 

"We've validated that we can ‘sleep' the STEMGEL™ with explosives for up to 30 days in contact with explosives.

"However a common driving motivation for many mines to test us is the environmental aspect of dust control along with fragmentation."

Potential savings

Shockwave recommends a three-phase approach to trialling its technology and welcomes people to its headquarters in Welshpool in Perth to see a demonstration of STEMGEL™ being loaded at their custom training facility.

"First we demonstrate it can be used safely under site-specific conditions," Trouchet said.

"Secondly, we do an on-site side-by-side blast to evaluate and compare STEMGEL™'s performance with the site's current methods.

"Thirdly, we start looking at the optimisation."

Aside from dust control and safer blasting, two further expected benefits include the improved fragmentation rate and potential savings in drill and blast costs.

"If we change the sub-drill height, or the space and burden, you can make on-the-bench savings immediately," Trouchet said.

"But that's not where the money bag is - that's in the digging ratio and fragmentation results."

Separate trials at different mine sites demonstrated that using STEMGEL™ created greater fragmentation and improved ore dig rates, by 14% - 17% on average.

"The bond work index - or effort to extract the ore - is a term we can quite easily validate in a blast," Trouchet said.

"If you had two holes side-by-side, one with aggregate and one with STEMGEL™ which creates all this micro-fracturing in the rock - you can't see it physically but when you go to crush it, you can crush it more easily.

"That means you need less energy, and it can lower your carbon footprint.

"In fact the initial sums we've done indicate that using STEMGEL™ causes about a 100 times less CO₂ emissions by volume of stemming in the hole compared with aggregate."

As for the gel itself, Trouchet said it virtually disappeared after the blast.

"The product is a blend of polymer and water and is indetectable in downstream processing," he said.

‘More bang for your buck'

Shockwave has made the commercial decision to work alongside drill and blast contractors, to enable them to use STEMGEL™.

"We see this as a market for explosives companies, to get their foot in the door at new mine sites," Trouchet said. 

 "Our expertise is to manufacture the product and the equipment and provide them to our authorised, licensed users.

"The reason we can do that is because we have a patent on the technology, so we have a certain amount of control."

Shockwave's GELDRIVE™ units are tailored to site specific requirements and load holes faster that aggregate stemming.

GELDRIVE™'s dual-hose system delivers the polymer liquid through an inner tube and water through an outer hose, with a static mixer combining the two as they enter the stem, where the mix sets in about 10 seconds.

Trouchet said switching to STEMGEL™ and using a GELDRIVE™ unit was similar to mine sites running aggregate or emulsion trucks, but GELDRIVE™ only needs water.

There was also the possibility for autonomous stemming trucks.

"We see it as the future, once people get their heads around it," Trouchet said.

"We get asked if we can become electric. The answer is yes.

"Can we reduce the carbon footprint? Yes.

"Can we become autonomous? Yes.

"We're changing the parameters around the blast.

"It's more bang for your buck, better fragmentation and greener from an environmental point of view."