By updating its machine guidance equipment as the technology evolves, a WA earthworks contractor is keeping ahead of the increasing demands of a local mine site.
At the Worsley bauxite mine and alumina refinery in the southwest corner of Western Australia, heavy haulage and earthmoving company, B&J Catalano has the contract to build settling dams to hold residue from the refining process.
The refinery produces more than 3.1 million tonnes of alumina annually, and for every tonne of alumina refined, 2.5 tonnes of bauxite residue is produced - so the volumes are not small and they are increasing substantially every year.
To optimise land use, one settling dam is constructed on top of another once the lower dam has dried out and its contents consolidated.
In places, eight or ten dams are built on top of another to a total height of around 40m. For structural reasons, each subsequent dam is built smaller in area than the one below it, giving the perimeter walls a stepped appearance.
With the additional requirement to incorporate underlying clay blankets, sand layers and networks of drainage pipes for the dams, the earthworks task is quite complex. And to keep ahead of residue production, dam construction often continues into the night.
B&J Catalano has been working at the site almost from the beginning of Worsley’s alumina production in 1984. In the early days, dozers were used to build the dam walls. Levels were set using pegs and each dam covered many hectares, so the work was tedious.
When GPS machine guidance became available in the 1990s, B&J Catalano immediately recognised its potential for their application and had their dozers fitted with Trimble Australia’s Bench Guide systems.
These systems were quite basic by today’s standards, but they did the job. In fact they are still doing the job, because B&J Catalano’s three D7 dozers still use Bench Guide today.
Around six years ago, when Trimble Australia released its SiteVision GPS machine guidance system, Catalano had the system installed on all four of its graders. Two of the four systems are set up for fully automated machine control.
More recently Trimble Australia has released its GCS900 3D grade control system. Keeping up with the technology, B&J Catalano had this system installed on the first of its Komatsu PC1250 hydraulic excavators early this year.
With an ever increasing workload, B&J Catalano has now had its second PC1250 fitted with the advanced GCS900 3D equipment.
Today the excavators do the complex work of shaping dam floors, while scrapers and the graders build the dam walls.
Both excavators are fitted with a Trimble MS980 GPS antenna on each back corner, together with solid state angle sensors on their buckets, booms and sticks to measure the precise 3D position of the tip of the bucket.
Each cab is fitted with a Trimble data radio that takes satellite signal corrections from the Trimble 5700 base station.
An on-board Trimble CB430 computer instantly calculates the bucket position and provides the operator with a display showing the bucket position and the design grade taken from a digital terrain model (DTM) in the computer.
According to Chris Chandler, B&J Catalano’s senior surveyor at the site, by working off a DTM every cut an excavator makes is right straight away.
“Once I’ve uploaded a design I can just say to the operator, “Off you go,” and he’ll do the whole thing for you,” said Chris Chandler.
“But it really comes into its own with complex shaping,” he said. “If a drain has to be excavated at the base of a stockpile or a bench built with different angle batters above and below, it’s quite straightforward,” said Chris Chandler.
Chris Chandler said the clarity of the screen graphics and the ability of the operator to see exactly what his machine is doing in cross section and plan view have a lot to do with the simplicity of operation.
“An operator can see the bucket reach out and bring it towards him at the design grade, just by looking at the screen,” Chris Chandler said.
“That allows him to plan the work himself and he doesn’t have to go screaming to the surveyors, saying, “I want to work this way, so put your pegs there.”
“Even at night he can see what’s going on, just by looking at the screen,” he said. Today B&J Catalano would find it virtually impossible to build the dams fast enough without Trimble Australia’s GPS machine guidance equipment on all nine items of earthmoving machinery.
B&J Catalano also has three GPS pole mounted Trimble SCS900 Site Controller Software systems, which the surveyors can use to get an instantaneous measure of earthworks progress.