August 2019

Into the void: managing abandoned underground mines

  • By Dr Joe Cronin, Australian Droid and Robot

A real-life case study showing how robotic technology can safely and efficiently carry out inspections in hazardous environments 

What happens to a mine at the end of its life? Ideally, as required by law and the mining lease, it is up to the mine owners to rehabilitate the site to make it safe for the land users and the environment. 

While the mining industry has great experience and technology to build and operate mines, there has historically been little investment in the development of technology to manage abandoned mines. An operating mine requires services to be maintained (ventilation, de-watering, etc) and regular inspection by qualified technical personnel to ensure a safe environment. Some of the abandoned sites have not had inspections or operating services for many years, which can make it hazardous for personnel to enter and survey the mine. 

This was the case at the abandoned Collingwood Tin Mine, tucked away in iconic Queensland rainforest 30 km south of Cooktown.

The Department of Natural Resources, Mines and Energy (DNRME), responsible for managing abandoned mines in Queensland, has been developing long-term management options for the Collingwood site, working closely with traditional landowners and the local community. When the mine was closed, a concrete plug was constructed in the decline, 180 metres in from the portal. DNRME needed to inspect the plug prior to formulating a design to permanently close and remediate the entrance. This was a challenging task, as it was too hazardous to send personnel into unventilated and unsupported ground to conduct the inspection. As the DNRME Abandoned Mines Team are constantly faced with unique challenges, they are always ready to trial new technology.

This was the backdrop for DNRME to contact Australian Droid and Robot (ADR), a Brisbane-based company specialising in the development of robots and drones for underground mine inspection. We have spent a decade developing our technology to address exactly the sort of challenge faced by DNRME, and were excited to showcase our systems and equipment. 

But we were apprehensive at the same time – this would be the first time there would be absolutely no chance of recovering our robots if something went wrong. Our systems needed to be 100 per cent robust.

Because the conditions of the decline were not understood, we decided to send in ground robots to minimise the impact. The most challenging aspect of remote inspection is maintaining strong, high-bandwidth communications for control and video feedback. ADR robots are connected via a military-grade Rajant dynamic Wi-Fi network, which allows each robot to act as a relay node in the network. This means that as each robot moves into the mine, the signal is automatically reconfigured to bounce between the robots to find the strongest connection back to the base station. This increases the range that the robots can enter the mine and allows them to operate out of line-of-site of the base station. 

‘There has historically been little investment in the development of technology to manage abandoned mines.’

Each robot has independently driven wheels with independent suspension and traction control to maximise mobility in underground terrain. We have also developed our own control hardware and software for the robots, which can operate over existing mine Wi-Fi or the dynamic Rajant network that is deployed in real-time.

The ADR robots being cleansed in a traditional warming ceremony.

Prior to entering the mine, DNRME and ADR participated in a warming ceremony conducted by Marilyn, one of the traditional elders and landowners.

The date of mine closure etched in the plug.
The Australian Droid and Robot underground vehicles in the decline.

Taking part in the warming ceremony was an important part of the process, making us feel more calm and connected to the local country – we were very thankful that Marilyn took the time to cleanse our technology. 

The inspection went off without incident. After sending in smaller relay robots, the team sent in ‘Dropbear’, our ground robot fitted with a high intensity light and high definition camera. 

The resulting video showed the plug to be intact, with water flowing over one side. The camera was powerful enough to pick up a section of the plug where those who constructed it had scratched the date and their names into the shotcrete. These were probably the last humans to have left the mine.

For ADR, the inspection proved to be a great way to demonstrate our technology and to help DNRME move further along with their closure plans for the site. 

Ben Brassington from DNRME and Tom Watkins from ADR next to the ‘Dropbear’.

Conclusion

It will become more hazardous to extract resources in the future, as mines become deeper and grades become lower. From continuous convergence monitoring to rapid re-entry after seismic events, robots will play an increasing role in mine operations. The ability to conduct remote inspections without putting personnel in hazardous areas will become a necessity. Even though the industry has made great gains in automating production, we still have to shut down operations to send humans in to conduct crack mapping, drawpoint and stope inspections and sampling. ADR is looking beyond automation to where we can send in robots and drones to execute tasks currently being performed by humans. In the future, tech services personnel will sit alongside the remote operators in the control room while they collect samples and conduct inspections remotely. This represents ‘Safety by Separation’ where the operator and the hazard are not occupying the same space. 

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