High Precision Machine Guidance Applications
It is well known that GPS guidance can vastly improve the efficiency of large scale earthmoving operations. However, less widely known are the countless hidden benefits of this technology and in unearthing these, we have only scratched the surface. Following are some of the benefits experienced by APS customers.
Finding Edge of Coal
Collinsville Mine in Queensland uses dozer stripping followed by an excavator truck fleet to uncover high grade metallurgical coal. The mine operates in a series of strips, pushing overburden from above the coal in each strip into the previously mined adjacent strip. The use of dozers is a highly cost effective form of overburden removal. However the dozers necessarily obliterate all signs of the previous strip and make the task of finding the edge of coal difficult. Typically the excavators are required for the last 10 to 15 metres of overburden above the coal seam. This material is moved in 2 or 3 benches. For efficient operation, it is essential that on each bench the material is excavated to the correct position to form the waste slope. If the excavators don’t go far enough, then coal will be wasted, if they go too far then the unnecessary rehandling of material adds to cost. Careful survey work before and after installing GPS guidance on the excavators showed that overexcavation was cut from 3.2% to 0.5% and underexcavation from 1.7 to 0.0%. These numbers represent very considerable cost savings to the operation.
Selective Mining
Century Mine in North Queensland mines several grades of zinc ore. In the pit, waste material and the various grades of ore are visually indistinguishable. Prior to installing GPS guidance on the excavators, geologists and surveyors were required in the pit at all times to mark out the ore boundaries with spray paint cans. Installation of machine guidance has not only increased the accuracy of selective mining by substantially reducing dilution and improving ore recovery, it has also improved safety by eliminating the need for personnel on foot around the large equipment.
Flatter Benches and Smoother Ramps
A side benefit noted at Century and other mines is that benches completed by machines equipped with high precision GPS are noticeably flatter and more even. Ramps are dug at a consistent design grade. This has major advantages for haulage as the trucks cycle faster and spillage is greatly reduced, thus improving tyre life. Consistent ramp grades mean that trucks do not change gear on the ramps, again improving tyre life and reducing damage to the road surface.
Drainage Ponds and Other Structures
With high precision guidance, completing excavations to design is easy. Mistakes and rework are largely eliminated. Ponds and drainage diversions can be built exactly as designed. Moreover, APS logging software will capture the positions of the ground engaging tool (excavator bucket teeth, dozer blade or scraper bowl for example) enabling an as built electronic model to be constructed. This can be exported back into Vulcan or other mining design software.
Mine Reclamation Work
Engineering trials have shown substantial benefits from using high precision machine guidance on regrading previously mined land. Machine guidance ensures that operators never push below final grade. With a good picture of how far off grade the work is, the operator can plan efficient pushing to get to design. Traditional methods involve bulk regrading first followed by survey followed by more bulk pushing followed by more survey followed by detail work later. Performing everything in one step is much faster and more productive. Engineering studies showed a 42% reduction in dozer hours per hectare.
