September 22, 2017

Drones to advance blast design and quality

Explosives and blasting technology leader, BME, has established a High-Tech Services unit to advance the application of drones in mine blasting activities.

According to BME technical director, Tony Rorke, drones fitted with high-resolution cameras and guided by computer systems using global positioning system (GPS) survey data have proved invaluable in improving blast quality.

“Our dedicated team applies a range of modern technologies like drones to help us plan, monitor and execute blasts in ways that optimise our clients’ results,” says Rorke. “The downstream impact can be felt in a range of benefits to mining productivity – such as finer fragmentation, higher digging rates and reduced power consumption in mine crusher circuits.”

While great strides had been made in surveying and drilling blastholes, he said, a mine’s survey plan is often not completely accurate or up to date – potentially reducing blast quality.

“Using drones, we can generate high-quality aerial imagery of the blast site after holes have been drilled, capturing the exact GPS coordinates of each hole,” he says. “The position of each hole is surveyed and then marked so that it is easily identified in the footage from the drone as it passes overhead.”

The actual blast-hole positions can then be referenced exactly to the survey coordinates of the mine – to allow accurate measurement of the variables necessary to plan an optimal blast.

“The coordinates are exported into our blast timing design program BlastMap III and into our AXXIS electronic detonator system – so that the appropriate firing sequences, timing and charge distributions can be applied to the blast, based on the exact positioning of each hole,” says Rorke.

He emphasised the benefits in being able to adjust the timing of a detonation in a blasthole – as well as firing sequences and charge distribution – to take account of any slight divergence of a hole’s actual position compared with its place on the survey plan.

“Unless we measure, we are only guessing; so better measurement – both before, during and after a blast – is the key to optimising blast results,” he says. “Drones advance our measuring ability greatly when combined with BME’s other innovative in-house tools like our blast planning software together with our electronic detonator system.”

The versatility of a drone as a vehicle for the camera also extends to valuable monitoring functions during and after the blast. What experts can take from the images and graphics is a clearer understanding of what block faces look like, and whether there is any damage or potential problems resulting from the drilling.

“Sampling, measuring and quantifying the fragmentation achieved by a blast is much easier when done from an aerial scale image that a drone can deliver, making the analysis much more useful in improving future blasts,” he says. “The distribution and volumes of fragment sizes are important to monitor, as these are vital to continuous improvement strategies.”

After a blast, drone images from above give a much clearer picture of where coarser and finer fragments are lying – and in what relative quantities.

“It may even be possible to use the images as a basis for actually measuring fragment size in a more scientific way,” he says. “We currently take post-blast photographs but it is difficult to interpret these in a way that is statistically valid.”

Software now also allows the creation of a three-dimensional surface of the blast block, by combining the aerial drone imagery and the face profile footage from land-based cameras.

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