Over the years, technology has transformed most aspects of mining: the way we mine today is very different from the way it was done a century ago. Nevertheless, one thing that has essentially remained the same is the “drill and blast” method of creating tunnels in most hard rock mines, where holes are drilled a set distance apart from each other, loaded with explosives, the explosives are set off, the blasted broken rock is removed, and bolts and screen are used to secure and support the newly created section of tunnel. Then the process starts all over again to create the next length of tunnel.
The drill and blast technique has its risks, and from a productivity point of view, can cause delays at shift changes when employees must vacate the area during the blasting and rock removal. And although the equipment used for drill and blast has improved over the years, the basic concept has stayed the same – until now.
‘Improve safety, increase productivity…’
A ground-breaking new project is underway at Garson Mine in Sudbury, ON to test a new continuous mining machine (CMM) that will take over the job of building tunnels in hard rock. “A couple of years ago, we started looking at mechanical rock excavators (MREs) as a way to improve safety, increase productivity and potentially reduce costs,” explained Andy Charsley, principal mining engineer, based in Copper Cliff. “We asked: ‘Can we do this safer, faster, cheaper than we’re doing it now?’”
Following a return to Sudbury after six years at our Voisey’s Bay operation in Labrador, Andy was asked to lead a project to test an MRE at Garson’s McConnell ore body. “We chose McConnell because it’s a ramp-access mine, as opposed to most mines which are shaft-access,” said Andy, “so we can drive the machine right in from the surface.”
Continuous mining machines have been used for years in soft-rock applications, such as coal, potash and salt mining, but using a machine designed to continuously bore through hard rock, in a mining application, has not had success.
“There are large circular machines that can bore through hard rock in fairly straight lines – think of the tunnel under the English Channel,” said Andy. “They’ve been around since the 1960s, but are not suited to mining, where we need a machine that can cut in different directions. It’s only been in the past 10 years that the bigger mining original equipment suppliers (OEMs) such as Komatsu, Epiroc and Sandvik have been developing machines that can continuously mine hard rock.”
Test Down Under
In February 2020, Andy and his team chose to work with Komatsu, one of the world’s biggest industrial equipment manufacturers, to supply a machine and operators for a 400-metre trial run at Garson. Komatsu had been building a series of prototypes, and completed its first two commercial MREs. The Komatsu machines were built in Wollongong, a coastal city in Australia and then tested successfully underground at a nearby Australian mine in late 2020.
Each machine, which can be operated by one person, allows for continuous rock excavation, and is equipped with a conveyor belt through its centre that carries the broken rock pieces to a scoop behind it. The scoop, controlled by a second operator, is tasked with taking away the rock pieces. Technical and Engineering support will be on standby to troubleshoot throughout this prototype trial.
Off to Garson
With the success of the test in Australia, Komatsu’s second machine was shipped in sections to Garson Mine in early 2021. Currently, it is being assembled and will be ready to cut rock by April, Andy said.
Although progress is expected to be slower at first as production is ramped up, the MRE is expected to eventually cut through about 3.5 metres of rock per shift. At that rate, the 400-metre trial should take about nine to 12 months, and continue into 2022. Andy, who has been with Vale for 20 years, starting in the Mines Research Department, will work with the Garson Operations Team to assess the success of the project during the trial.
“We want to see if we can improve our commercial rate of cutting. We will be able to quantify the cost per metre of cut rock as well, to compare it to the drill and blast method, and of course we’ll examine the safety and sustainability of the new process.”
The results of the trial project will inform the business as to whether to continue using the MRE at Garson, and to determine if the advantages of using MREs allow hard-rock mining operations to complement the century-old drill and blast method. “We want to find out what this looks like for the future of mining,” he said.8