Level E48 North Parkes Mine
UEA Civil and Mining was commissioned to undertake an ambitious challenge in 2008 utilising relatively new terrain levelling technology. In a world first UEA took its Vermeer T1255 Terrain Leveller underground for a roadways project at North Parkes Mines, part of Rio Tinto’s Australian operation.
The project required the use of terrain levelling machinery to mill down the series of roadways that make up Level E48, one of the major production levels in the North Parkes mine. These roadways, when finished with a 400mm concrete capping, are designed to carry a fleet of underground remote controlled loaders until the “cave-block retreat” mine reaches the end of its life several years in the future.
The main consideration was the size of the terrain levelling machine and the inherent risk of taking something that big down the kilometres of underground roadways. The machine at its widest part is 3.7metres and most of the roadways were not much wider than 4.5metres. The length of the machine being 14metres meant that the series of corners to be negotiated to make the descent had to be well planned to ensure it would be achievable.
In June 2008, UEA mobilised the Vermeer T1255 Terrain Leveller to the North Parkes site and went through a series of modifications, most of which focused on reducing the extremities of the front of the machine and the removal of the shroud surrounding the drum. Great lengths were taken to create a series of safety procedures to mitigate the risks of operating the machine in this unique environment. Two weeks later the machine made its successful descent to Level E48. At least once, the terrain leveller had to cut its way around a corner and on numerous occasions there were only millimetres between the machine and the rock walls.
The ground conditions consisted of some road base, but the majority of the material to be milled was ore of approximately 90 MPa. Also encountered were seams of porphyry of up to 200 MPa. This ran in a vein through a number of drives and proved to be very difficult to cut. A call was made to persist with the milling operation as the alternative of drill and blast would disrupt the on-going mining operation in the adjacent workings. Most of the drives were approximately 200 metres long and could be completed in a single 6 hour day shift. Because a laser was used to keep grade, the depth of cut varied from shallow cuts of 150mm when the ground level was low (or the machine encountered the hard porphyry) to 800mm at times when in the ore or the profile was too high. Cutting times varied from less than 1metre/minute in the porphyry to 10 metres/minute in the ore.
The entire project took about two and a half months to complete. The saving in time and more importantly the absence of any lost time injuries for North Parkes Mines were invaluable. The project also highlighted the fact that when a good working relationship is formed a successful result can be achieved; it has also set a new benchmark for the safe and efficient production of similar projects.
For further information on this project please contact Dominic Hallam.