Automation seems to be the industry’s current ‘buzz word’. Minesites wishing to increase productivity by rapidly advancing mine development are looking to their drill rig manufacturers for guidance and consultation on how to get the best out of their equipment.
While several mines promoting “rapid development projects” have hit a few speed bumps of late, Cadia East in New South Wales has enjoyed calm waters, sailing towards what is said to be the best advance rate worldwide for screen supported decline in a calendar month.
The Newcrest Mining gold-copper project’s four panel crews completed 311 m of development in May, passing a new advance-rate milestone in the proverbial home stretch of the project’s pre-feasibility decline development.
According to Cadia East’s project manager Stephen Powell, the result for the month was 311 m comprised of 278 m of decline face advance plus 33 m for stockpile development.
“The next best in Australia was about 270 m comprised of 210 m of decline plus 60 m of other development,” he said.
“The real critical path is decline face chainage, of course, so 210m falls well short of 278m.”
Powell credited the milestone to a motivated and hard working crew, good rock and a great cultural environment in terms of people living locally.
There have been no lost time injuries in some 1400 days of work on the project.
“On a single heading, with small crews, the best equipment, repeatable work practices, a focus on process control and a strong sense of urgency, with everyone working as tight-knit team, we’ve been able to achieve consistently good results,” Powell said.
“Achieving and sustaining a very high standard of maintenance, from training and retaining skilled personnel, to disciplined execution, is extremely important in rapid development. Having good equipment to start with is important, but you really can’t afford to have your front-line gear break down.
“We’ve also had quite a lot of technical input from an engineering level, which we recognised early as a key requirement given the unconventional equipment we’re operating and the targeted development rate of 8 m per day.”
Newcrest cut the Cadia East decline portal in May 2005 and has been developing the decline for three years in what is a precursor to a full feasibility study set to get underway later this year and, all going to plan, development of what could become Australia’s biggest underground mine.
The proposed panel caving operation, Australia’s first, is targeting an annual ore production rate of 24 million tonnes per annum.
Establishing an access decline to obtain vital technical information and bulk metallurgical samples provided Newcrest with the opportunity to test run a rapid development approach which combines leading-edge tunnelling methodology and mine-specific equipment and technology. Long-round drilling, high-powered drifters, automated drilling, emulsion charging and high-capacity load-haul are key elements of the Cadia East rapid development approach.
Success with the approach over the 7 km of decline (and other) development, to a depth approaching 1 km, is seen to offer leverage for an approved project in terms of the timeframe and resources required for implementation, and longer-term leverage in the form of a proven rapid advance strategy for future projects.
“Significant investment advantages have been recognised in establishing rapid development at Cadia East,” Powell said.
“It allows timely completion of the pre-feasibility study through development of the decline and bulk sample drives. Rapid mining techniques could then be employed in future development to reduce lead time in mine establishment and enhance net present value calculations of Cadia East and other projects.
“This is especially pertinent in capital intensive mining methods, such as block caving, due to significant up-front expenditure prior to production.
“It hasn’t all been rapid development because we didn’t take delivery of the big [Atlas Copco L2C] jumbo until the middle of 2006 and didn’t start using it fully until September that year,” Powell said.
“Our previous best monthly development mark was 283 m [in December 2006], comprised of 245 m of decline development plus 38 m of other development.
“I think 300 m plus in a 31-day month is a stretch. We’ve had a good run, no doubt about that. But it’s been hard going.
“We’re coming to the end of our single-heading run in September this year. It’ll be multi-heading from that point. So we’ve just about run our race in terms of this current development phase.”
Powell said Six Sigma improvement processes had supported the adoption of emerging technologies at Cadia East.
Over the past decade it became evident technological improvements developed in the European tunnelling industry offered potential for rapid tunnelling in mines. Newcrest and others have proactively engaged with equipment manufacturers to adapt the technology to Australian mine conditions and, at Cadia, into a new integrated tunnelling process.
The emerging technologies included new generation high frequency drifters offering increased drill penetration rates, longer feed lengths allowing cuts of up to 6 m in depth, and laser navigation, automatic boom control and face pattern software to provide more accurate drilling.
Atlas Copco’s underground drill business line manager Stevan Topalovic told Australian Mining that Cadia came to the Atlas Copco with a request for a machine that had the ability to rapidly develop the mine.
“We delivered a machine that would supply them with 50% automated drilling,” he said.
However, using clever engineering processes they achieved 70% automation. They were determined to get maximum amount of value out of the machine and, in doing so, exceeded everyone’s expectations.”
According to Topalovic, automated drilling is the way of the future. Automation drill rigs improve accuracy, speed and the occupational health and safety hazards that are present when operating the machines.
“Today, computers are faster and more precise than human operation, and for that reason more and more miniesites are leaning towards automated machines. They can get the results they want first time, everytime,” Topalovic said.
But it isn’t just the introduction of automation that has simplified the operator’s role. Overall machine design has been invariably simplified.
“Ten years ago, operators had to navigate their way around a variety of steering wheels and gears. Today, operators can navigate a machine using joysticks,” Topalovic said.
“The younger generation looking to break into the mining industry can reap the benefits of the boom because these machines are easier to use than ever before.
“New operators can understand and deal with an electrical system better than a hydraulic system,” he said.
Beyond the benchmark
On the Cadia East project, the partly automated drill rigs allowed the team to achieve working goals ahead of target.
Cadia East’s advanced tunnelling drill, the Atlas Copco L2C30, was equipped with Atlas Copco COP 3038 drills which had a 50% higher penetration rate than the manufacturer’s predecessor COP 1838 drills.
Drill rate comparisons between the COP 1838 and COP 3038 during the project highlighted the increased production capacity of the new generation drills. Over five months from January 2006 to May 2006 the mean duration for the drilling component of the cycle using the COP 1838 (4.2m-long) rod was 2.7 hours. Over a similar time frame, between October 2006 and February 2007, using the COP 3038 (6.4m) rod, the drilling component was 3.1 hours. This meant a reduction of 14 minutes per metre of advance, or a 77 minute saving on a 5.5m cycle.
Advanced boom control allows full automation over a significant area of the face, while navigation of drill rigs, once undertaken with suspended chains, paint cans and a deft eye, now employs direct laser alignment techniques that use boom mounted targets to orientate the drill rig in space with direct input into the boom control system. This ensures all holes finish on the same plane regardless of the unevenness of the face, and primers are aligned with the resulting initiation producing a very flat face which is virtually free of butt.
Use of emulsion explosives for faster charging, improved fragmentation, and reduced fume generation; and electronic detonators with improved perimeter control, resulting in reduced over-break and ultimately less scaling and fibrecrete use, complemented the high-speed drilling.
High capacity load and haul machines are under constant development by manufacturers.
Cadia East has matched the fastest, high-capacity loader and trucks available at the start of the project 20ton payload loader able to tram on a 1:7 roadway at 8kmph, plus 50 to 60ton payload articulated trucks able to traverse the same gradient at 11kmph in the first known Australian combination of these high capacity machines in a mine tunnelling application.
One-pass resin bolting and cable systems for intersection support; hydroscaling and semi-automated fibrecrete application; and a fibrecrete mix with improved additive chemistry (for early strength/faster re-entry) have also been used.
“Accurate long-round, high-performance drills coupled with emulsion explosives and high capacity materials handling have demonstrated single heading tunnelling rates over 9m per day are now practically possibly,” Powell said.
“This is about 50% above the previous Australian benchmark of 6m per day and augurs well for this and other deep mine developments in future.”
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