Technology optimises drilling and blasting

By Freya Purnell

Improving blasting techniques
Duncan Chalmers, senior lecturer in blasting, University of New South Wales (UNSW), said one of the most significant areas of change in blasting is a move away from working from standard patterns, assessing and empirically modifying the pattern, particularly in more marginal areas where blast performance is critical in producing low value ore. Instead, engineers look at the geotechnical nature of the ore body or waste rock, and use a rating of its rock mass to better distribute the energy through the rock mass, providing better fragmentation. This can be achieved through the use of different explosives, matched more closely to the material being blasted, or through altering the spacing on the pattern.
“If anything, we’re introducing a lot more science to it than art,” Chalmers said.
“The immediate benefit is that there’s a better distribution of particle size through the rock mass so you then get a better throughput through the mill, better loading characteristics, a reduction in need for secondary breakage, and more even loading on the trucks.”
He added that because there is less wasted energy during blasting, there is usually less ground vibration and noise - which provides both environmental and economic benefits.
Another modelling project is currently being undertaken by the CSIRO, researching blasting models for low-density explosives.
Dr Gary Cavanough, senior research scientist, earth science and resource engineering, CSIRO, said the project leverages software generated through research at overseas universities to model blast curves and pressure, and then show how these will react with a specified rock mass, illustrating how the rock will break. While these models have been generated using normal explosives, Cavanough is now working on developing information on the effects of blasting with low-density explosives, which contain a proportion of inert material such as ground rubber.
“With low-density explosives, there is a large amount of gas involved and a slower application of force. You don’t waste as much energy, you get better fragmentation and when they blast, it throws rock away from the face,” Cavanough said.
To generate accurate information to feed into these blast models, the CSIRO is creating sensors to measure shock wave pressure and temperature. The first round of test-site experiments have now been done, with pressure transducers successfully tested. The researchers are currently refining a design for temperature transducers, and once this is proven, they can gather information through testing to feed into the low-density explosive blast models.
There are definitely gains to be made through the efficient use of low-density explosives.
“It’s probably more applicable to coal mines for clearing overburden, but they could save hundreds of millions of dollars a year for each mine if they can knock off just a fifth of their explosive usage,” Cavanough said.

Optimising drilling
While Cavanough said there has not been a great deal of research in drilling to date, this may soon change. The CSIRO is currently establishing a Deep Exploration Technology Cooperative Research Centre (CRC), which will include a Drilling Technology Programme, bringing together researchers from the Universities of Adelaide, Western Australia and Curtin University of Technology and CSIRO with suppliers of drilling technology.
Some of the projects which have already begun as part of the CSIRO’s Minerals Down Under flagship are investigating performance optimisation of the drill rig and using drill bit steering to achieve straight holes for underground mines.
“Rotary percussive drilling is hard to control, so we have a method where you put a pressure wave pulse onto the drilling feed pressure, and you use a radio demodulation signal extracted from the rotation pressure,” Cavanough said.
Using this control system allows for faster, more effective drilling.
When drilling up holes underground, the effect of gravity results in the drill wandering and hitting rock faults, so the CSIRO is working on a method to steer the drill bit.
“As the drill is spinning, a sine wave pressure pulse is applied. The maximum pressure is applied when the drill bit is in a certain position, and by shining a laser up the centre of the drill rod, you can see if it is drilling straight,” Cavanough said.
These projects will be transferred to the CRC, which has received funding of $100 million over eight years and a test site donated by the South Australian Government, when it is up and running. The aim is to enable the developments through research to be transferred straight into the field via industry partners.
Cavanough is hopeful regarding the potential to maximise effectiveness of drilling and blasting tools.
“There’s a lot of research to do, there’s no way we’ve reached the end of the line as far as how we can go with the existing equipment,” he said.