Overcoming mining oversize problems

Most underground mines throughout Australia and the rest of the world face the challenges of moving oversize ore at some point in a mine's life.

Whether that oversize is created from slabbing of the hanging wall, inaccurate drilling, or just not enough autogenous grinding in the case of a block cave, large rocks can be very costly and extremely dangerous to deal with.

The cost can be created by several factors; actual cost and frustration in dealing with the oversize, cost in terms of lost production from the mine, and even the cost of walking away from a stope in extreme cases.

In Australia more than 85 per cent of our underground hard rock mines use bulk mining methods such as long hole open stoping, sub level caving or block caving.

Each of these common mining methods is susceptible to producing oversize material which can represent major challenges to the mine operator.

The mining method deployed typically determines where the oversize material presents.

In block caves and sub level caves it is typical for oversize to present at the draw point or in fact above the draw point, essentially closing the draw point until the material is dealt with.

Whereas in long hole open stopes it is common for oversize to appear inside the stope, blocking remote LHD (load, haul, dump machinery) access altogether and stopping, or at best, restricting production.

In any of these locations the oversize material must be removed before safe and efficient production can resume.

This requires remote capable equipment to be used to ensure personnel are removed from the area where the material is being blasted, with either water or explosives, or fragmented by a rock breaker. In each of these cases there is a risk of rock fall or material rush as the blockage is removed.

Some years ago MacLean Engineering recognised the problems and restrictions created by oversize material in mass mining methods.

Because there was nothing available within the market place designed to specifically deal with this material the company went about designing its own fleet of what it termed "Ore Flow Products". They have since gone on to develop a mobile rock breaker, a 10 000 litre capacity water cannon, and a range of secondary breaking drills.

According to MacLean Engineering "the secondary breaking drill is fully functional on remotes, including tramming, to allow the self-contained machine to be moved into a stope unmanned then drill and charge an oversize piece of material for breaking, ensuring the safest and most efficient resumption of production possible".

All of these units are available as remote capable and have been developed with remote partners Hardline Solutions to provide the optimal solution for this complicated application.

MacLean focused on hard rock innovation by providing a self-contained unit, with onboard air and water, along with their machine remotes. They have even worked with several different explosives suppliers at different locations around the world to provide remote hole charging capabilities using different explosives mediums such as Power Gel, ANFO and Emulsion to charge the drilled holes.

However even the most planned and thought out operation can still have dire consequences when dealing with hang ups and material in rush. So even with all personnel removed, the machine itself is still always at risk.

For the worst case scenarios they offer remote retrieval capability should it be required.

Their secondary breaking drills come in a range of configurations designed for different applications with a reach ranging from five, six and up to nine metres in vertical height.

According to the company they can be specified to fit into a profile as low as 2.2 metres high with an even lower version being worked on currently, while still maintaining both their FOPS and ROPS certification.

A 900 litre on board water tank, self-contained flushing air, diesel drilling and seated operator's position while tramming and operating ensure the unit is the safest, most productive and reliable available demanding applications in hard rock mining. 

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