Delegates from around the world share deep mining solutions
Deep Mining 2014, held in Sudbury September 16 to 18, was a big hit, attracting 302 attendees from around the world.
“It was an overwhelming success,” said conference co-chair and Laurentian University associate professor Marty Hudyma. “We really didn’t know what to expect in view of the fact that the industry is in a downturn. We were optimistic that we would get 200 delegates, and 250 would have been beyond our wildest dreams, so we were ecstatic with 302.”
According to Hudyma, approximately half of the delegates were from outside the Sudbury area, including contingents from Australia, South America, Europe and South Africa.
Deep Mining 2014, the seventh International Conference on Deep and High Stress Mining, was hosted by the Australian Centre for Geomechanics. It attracted 62 papers on a wide variety of topics including ground control, seismicity, ventilation, mine design and logistics.
“The feedback I got from delegates was that there were a lot of very good case studies on deep mining and the challenges they have to deal with,” said Hudyma.
“There are three real challenges. The first is the ground conditions and the stresses are getting more difficult, so we have to modify our mining practices to be able to work effectively and safely at great depth. The second is heat. In some mines, the rock face is 40, 45 and 50 degrees Celsius, so the environment that miners have to work in is so much more difficult than it is at shallower depths.
“The third challenge is getting people down there and getting them back. When we go down to three kilometres, the travel time can be in excess of an hour from surface to the workface. Moving large amounts of material from underground to surface becomes more difficult, so logistics and material handling are also challenges.”
One specific problem with mine shafts at great depth is that the weight of the wire rope and the conveyance exceeds the lifting capacity of the hoist, said Hudyma. In order to go down three kilometres with a single lift shaft, “we have to think of ways of reducing the weight of the rope as well as the weight of the cages and skips.”
Several presentations addressed this issue, including one on research that CAMIRO is overseeing on the use of a synthetic rope alternative.
A full-day workshop on rock bolting held the day before the conference focused on novel ground control solutions for deep mines.
“There are two problems,” said Hudyma. “One is rock bursting. The other is squeezing ground. We may start off with an excavation that’s 4.5 metres wide, but that excavation may actually close by a metre over a period of a month, so by the time it’s finished, it’s only 3.5 metres wide.
Our existing reinforcement can’t deal with that amount of deformation. It will break or separate from the rock, so developing reinforcement that will hold the rock back and at the same time be able to yield has become very important for some of our deep mines.”
In an opening address, Samantha Espley, Vale’s director of mines and mills technical services, described the conference as an excellent opportunity for delegates to network and learn from each other.
“We’re all dealing with the same problems and we don’t have the answers,” she said. “We’ve learned a lot, but there’s no silver bullet.”
Vale, which sent 30 delegates to the conference, has a special interest in deep mining as its Creighton Mine in Sudbury is now down to 8,070 feet (2.5 kilometres) with plans to continue mining to a depth of 10,000 feet.
State-of-the-art seismicity monitoring, destressing practices and the use of dynamic rockbolts have been effective for Vale, but as mining operations continue to depth, the company will have to look at smaller openings, smaller equipment and increased mechanization to keep workers away from the face as much as possible, said Espley.
Destressing is performed by drilling longer, additional holes to destress the ground in front of a heading. “You’re pushing the stress further away so you don’t have anything spitting or popping at you,” explained Espley. “We’ve been doing it for decades and figured it out through trial and error, but we’re learning more about it and getting to the point where we can use numerical modeling tools to potentially employ it on a bigger scale in big production stopes.”
Seismicity monitoring has also come a long way.
“Our systems are the best in the world,” said Espley. “They give us accurate realtime information on seismic events. You can look at the wavelengths in time sequence and understand what kind of event it was and what triggered it. We also have a virtual reality lab at the mine that allows us to look at the geology, the seismicity and the mining activity to understand an event and predict what will happen in similar circumstances.”
For Doug Morrison, president and CEO of the Sudburybased Centre for Excellence in Mining Innovation (CEMI), Deep Mining 2014 was an excellent opportunity to promote its Ultra Deep Mining Network.
With $15 million in funding from Canada’s Business-Led Networks of Centres of Excellence program and promises of an additional $31 million in cash and inkind contributions from the private sector, CEMI is rolling out a research program that will focus on rock stress, energy consumption, material handling, development rates and cooling.
“To bring together that number of people with so much expertise from around the world was a fabulous achievement,” said Morrison. “It was one of the best conferences we’ve had.”
