The collapse of mines has long been a hazard in the industry – and it’s one that continues to intensify as mining moves deeper underground. In October, an explosion in a coal mine in Turkey left 41 people dead. Earlier that month, a bauxite mine collapsed in Greece, killing one person; in September, a mine collapse in Illinois led to the destruction of a nearby high school; and in July, ten people were killed and six left injured in a mine collapse in China’s northwestern Gansu province.

There is no magic bullet when it comes to mine collapses – but developing the right technology can help limit some of the dangers posed to human life. “As resources become more finite, we’re having to go deeper and deeper, and the risk just keeps elevating”, says Callum Macdermid, head ground robot engineer at mining solutions company Australian Droid + Robot (ADR). “But we can reduce that risk through robotics.”

ADR was established in 2016 by underground mine automation experts, Dr Joe Cronin and Dr Dawid Preller. The company’s motto is “safety by separation”, an ethos that emerged out of Cronin’s recognition that some mining hazards are simply unavoidable – which is why it is vital that we remove the human element, wherever possible. As Macdermid explains, “The mining industry has a structure for doing risk analysis and risk assessment – it’s called the hierarchy of controls. Coming out of that industry, our co-founder was adamant that there needed to be another control added to that hierarchy, which was separation. And that’s what we really strive for – if you can’t eliminate the risk, let’s separate the human from the risk.”

The machine of the moment

ADR’s core product is the Explora XL, a “fieldhardened and field-proven Unmanned Ground Vehicle (UGV)”, Macdermid explains. “It’s a highly mobile, eight-wheel, multi-purpose platform with traction control and independent suspension, which provides a lot of agility. The overall design allows for any sort of payload to be installed on top of it, from gas sensors to inspection cameras – either optical or thermal – all the way up to a 3D LiDAR scanner. And you can integrate any of those with the platform and get the data back to wherever you’re operating the robot from.” Theoretically, the operator could control the robot from anywhere in the world – provided they have a 4G connection.

Fundamentally, then, the Explora XL is built to be robust and reliable – these, as Macdermid says, are the key qualities when it comes to designing robotics for mining – but it’s also adaptable and very user-friendly. “It is all controlled through an off-the-shelf gamepad controller,” Macdermid explains. “The software and controls are meant to be intuitive to use. So, if anyone has played a carracing game on an Xbox or a Playstation, they’ll be able to operate this, no problem.”

The hardware is straightforward enough – the Explora XL is a hardy, agile and intuitive UGV – but how well does it perform in real-life use cases? After years spent refining the Explora XL in open-cut and underground mines – as well as on Brisbane’s suburban golf courses – ADR got the chance to put their platform to the test, when a limestone mine collapsed in the south-eastern US in August 2021. Cut into a mountain, the mine is one of the US’s largest underground room and pillar operations; the subsidence and subsequent air blast (which was estimated to have moved at 180–190mph) were so severe as to bring about the collapse of the mountain itself.

Shortly before the subsidence, the mine’s experienced crew had sensed that something was wrong and had evacuated the area. As a result, there were no fatalities or injuries, but the task of getting people back into the mine to survey the extent of damage – and to prevent further collapse – remained a challenge. The only option was an unmanned operation on a scale that had never been attempted before.

As Macdermid explains, the mine’s operators searched all over the world for a company that could do this. “There were a couple that responded, but they gave lead times of up to 6–9 months for the R&D required for this sort of inspection. And then they got in touch with us and we said: ‘We can be there in under a month’. We already had a fleet – so we shipped 10 of the Explora XLs over there.”

Up to the task

ADR’s prime objective was to undertake a comprehensive visual inspection and survey of the subsidence, to ensure that the blast had not caused any structural damage that could lead to further collapse. In short, this small fleet of robots had to determine whether or not the mine was safe for human re-entry.

ADR were confident that their Explora XLs were up to the challenge – but the mine itself presented logistical complications that they couldn’t have planned for. “One of the biggest challenges was communications,” Macdermid says. “This mine is over 100 years old and it had little to no communications inside. It only had AC power as far as about 100– 200ft into the mine. Otherwise, it was just flashlights on [the miners’] heads or lights on the loaders, and a leaky feeder system, which is effectively a communication system for two-way radio.”

To get around this, ADR had to build up a mesh network from scratch using the robots. As Macdermid recalls, “We would drive a robot in; park it up; then drive another robot in further; and relay information through all of the robots. We also had additional nodes through the entry to the mine. So, we ended up with about 10–12 hops, jumping between robots and nodes, to get back to us with the live video stream.”

Trying to locate the robots from above ground, within the complex structure of the mine, presented another challenge during the six-day operation. “It’s called a ‘room and pillar’ mine,” Macdermid explains, which means it is made up of “big square pillars, one after the other, all the way through the mine. So, when you’re a kilometre deep, and you’re just looking at pillar after pillar – well, you can only count so many pillars before you get lost”. Using LiDAR (light detection and ranging) technology, however, Macdermid was ultimately able to “pull up a live view and match the shape of the pillar up to the precise map that we had, so we were able to navigate from there”.

Record-breaking robot

ADR’s operation in the US is unofficially the world’s deepest remote inspection, reaching a record-breaking 1.8km into the mine. And while forging a path through uncharted territory is never easy, Macdermid says that, in the end, the operation “highlighted the fact that our Explora XLs are really field-hardened. We had robots operating for 8 hours a day, covering tens of kilometres. We validated that the Explora XLs are where they need to be for doing the dangerous operations that they need to do.”

Of course, there remains the possibility that a mine could collapse while the robots are inside carrying out their survey. What then? “If a giant rock falls on the robot and crushes it,” Macdermid says, “that’s great. Because that could have been a person.”

In the near future, Macdermid is confident that there will be a “huge push for robotics and automation underground – and not necessarily by removing jobs” and provides the example of a driver who operates a load within a mine. Using automation, Macdermid says, that drivers “could operate the load remotely, above ground, where they can sit in an air-conditioned office rather than being a kilometre and a half underground. And it makes it that much safer.”

There is no denying that some element of risk will always be present when it comes to mining – which is why the development of automated and robotic technologies is vital for the future of the industry. Having carried out the world’s deepest remote inspection, ADR is blazing the trail – now is the time for the industry to follow.

This article first appeared in World Mining Frontiers magazine.