Rio Tinto systems to speed mine excavations

Rio Tinto claims it could double the rate of mine excavation and improve safety with three new systems it plans to test in 2012.

The British-Australian mining group announced last week that it had finished the design and simulation of the first system – a horizontal tunnelling machine developed in partnership with engineering services provider Aker Wirth.

Some of the technology is based on that used in civil engineering to cut rather than drill tunnels, allowing continuous excavation instead of the conventional cycle of drilling, blasting with explosives and removing debris.

The new machines are part of Rio Tinto’s ‘Mine of the Future’ programme, which also includes autonomous surface mine operations and advanced mineral recovery – improving efficiency to reduce waste and energy usage.

Rio Tinto’s head of innovation, John McGagh, told The Engineer that the programme would enable faster and safer excavation of the bigger and deeper mines needed to meet mineral demand from the developing world.

‘What’s innovative about this is getting a system to leave you with a fully lined, operational tunnel or shaft,’ he said. ‘It’s not just cutting or preparing the rock. These things leave you with a useable tunnel or shaft at about twice the rate you can get at the moment.

‘This machine basically peels the rock off the face. It uses multiple cutters and pretty advanced hydraulics and control systems to forward advance.’

The 64m-long horizontal machine is designed to excavate a 5.5m diameter arched tunnel at a rate of 10m to 13m depth a day. The company is now preparing for full-scale performance trials at Northparkes copper and gold mine in Australia in 2012.

The company expects to finish designs for a second horizontal machine and a vertical shaft system using similar technology by 2011. The shaft-boring machine will excavate an 11.8m diameter hole and together with the debris-removal system will be 20 to 22 storeys high.

Future mines will need to be deeper to reach enough new mineral deposits to meet demand, with copper mines expected to be in the 1,500m to 2,000m range, according to Fred Delabbio, Rio Tinto’s general manager of underground mining innovation.

Conventional shaft-sinking techniques have changed little since the 1950s, he said. ‘In the past this wasn’t that big of an issue when you had shallow and small holes. The holes we’re talking about are 10m in diameter, so you’re moving more rock and it goes slower.

‘By changing the way you cut, you do less damage to the rock around the shaft so you don’t have to support it as much and you let the machine do the work. It elevates the skill set from doing the drilling to maintaining and operating a large tunnelling machine.’

When asked if the new system would require fewer staff to operate, he said: ‘It’s a misconception that to automate and mechanise you need less people. You need higher-skilled people but you have more people involved and you’re going faster and safer.’

The company would not reveal the costs associated with developing the new machines, although McGagh said they were not insubstantial.

‘The reason we’re doing this is the value in the package is extremely substantial,’ he added. ‘The value comes in many ways. While the financial value is highly attractive the safety value is also another driver.’

As global demand stretches the world’s mines to the limit, operators plan to meet the challenge with automated mega-sites the size of the UK. Click here to read more (subscription required).