Surface Mining: Selective mining of pay minerals
Deposit material and mineral raw material are used for a whole variety of purposes, as a basis for construction or as a source of energy. But how are they mined? Which methods allow rock of every kind to be mined selectively and cost-efficiently?
Drilling and blasting in mining, earthwork and rock operations are, quite simply, no longer “state of the art”. Surface mining offers a far more economically efficient and environmentally friendly solution, as it is capable of cutting, crushing and loading rock in one single working pass.
Surface mining: Direct loading
One of the most important features of the WIRTGEN Surface Miners is their ability to load the cut material directly onto trucks. WIRTGEN Surface Miners are designed for front loading or rear loading, depending on the model concerned.
On the front-loading 2200 SM, the discharge belt is mounted at the front of the machine. It can be slewed to either side and the discharge height adjusted as required. Depending on the size of the truck, these machines load the trucks either from the rear or from the side. The operator of the Surface Miner has a clear view of the truck.
Other models, such as the 2500 SM and 4200 SM, are rear loaders, their discharge conveyor being mounted at the rear of the machine. The conveyor can be slewed about 90 degrees to either side and the discharge height adjusted as required. The operator of the Surface Miner can swivel his seat to the right or left to ensure that he has a clear view of the truck.
Gently loading trucks with small-sized material
In all cases, the fine grained material cut by the WIRTGEN Surface Miner ensures that the truck body is loaded uniformly, continuously and completely. These loading characteristics allow the truck size to be selected as required. Trucks with aluminium bodies and increased payload can also be used under certain circumstances, for example.
- No material re-handling
- Direct loading onto trucks is usually the most economical method if the material is to be transported over distances of more than approx. 500 m.
Surface mining: Windrowing
When working in windrowing mode, the cut material is deposited directly behind the machine without using the conveyor. This makes the cutting process independent of any loading processes (onto trucks). However, the material must subsequently be re-handled by a front loader.
In many cases, the higher productivity achieved by windrowing as compared with direct loading balances out the additional costs incurred for renewed handling of the material (e.g. by wheeled loaders).
Moreover, this method does not give rise to any belt wear and does not incur operating costs for the conveyor system.
- No time lost waiting for trucks
- No belt wear / higher availability
- Higher production output than when loading with conveyors
- Larger lump sizes
- Greater selectivity when working steep and inclined seams
- Most economical method for transport distances of less than approx. 150 m when handled by wheeled loaders and approx. 500 m in scraper operation
Surface mining: Depositing the material laterally
Sidecasting the material means that a stockpile is produced by dumping the material from several cuts on a pile via the belt. Depending on the slewing angle of the conveyor belt, material from 3 to 5 adjacent cuts can be piled up. Depending on the height of the resultant pile, the material can easily be picked up again by a front loader.
- Material can be mixed as it is mined
- Stockpiling in the mine
- No time lost waiting for trucks
- Independent operation
The innovative technology cuts expenses for machines and personnel and saves a considerable amount of time when compared to conventional methods. At the same time, it produces even, stable surfaces and embankments, and permits the selective mining of individual rock layers. And that’s not all: Surface mining is a low-dust, low-noise method that causes no damaging vibrations and therefore permits effective mining of useful minerals close to residential areas or roads.
Cutting costs, boosting product quality and efficiency
The mined and crushed material is so small that it can be processed profitably, requiring minimum subsequent treatment. Mining bauxite, phosphate, kimberlite or salt has become increasingly profitable and the surface miner can even mine hard limestone or granite with unconfined compressive strengths of up to 260 MPa without blasting.