Tweefontein Optimisation Project (TOP) located 110km north east-east of Johannesburg in the Mpumalanga Province, South Africa, is currently being developed at approximately R8, 213 billion, is on schedule and on budget.
Glencore Coal’s Tweefontein Optimisation Project (TOP) is on schedule and on budget, once complete in the middle of the year, is set to employ 750 full-time employees mostly residing in the town of Ogies and surrounding areas in Mpumalanga Province. In addition, most of the employees are being redeployed from Tweefontein’s closing underground operations.
The organisation that continues to recruit employees from the surrounding communities, boast of a centralized training facility 10 km from Tweefontein, where mining operators and plant operators are trained.
The first two of a total of seven openpit operations are already producing at the operation, which is on the way to becoming Glencore Group’s second largest coal operation after Optimum Coal.
Tweefontein Mine Infrastructure
Currently under construction is a big eight-bay workshop, including a tyre handling facility, a million litre fuel and lubrication service station, offices and a dragline section.
In addition, infrastructure that has been completed include a R3.5 billion double-stage cyclone coal plant, designed and build by DRA House Projects as well as the rapid loadout facility that feeds the rail siding that connects the mine to the Richards Bay Coal Terminal.
Operating infrastructure worth R2-billion, which includes a high volume tip that feeds a run-of-mine facility designed to handle pillared coal, has been completed along a dyke to avoid the sterilization of coal reserves.
Close on 800 giant precast concrete culverts, three-and-half metres high and just over five metres wide, were deployed in the construction of two buffer (stockpile) tunnels.
Manufactured by Concrete Manufacturers Association (CMA) member, Aveng Manufacturing Infraset, and designed by the company’s technical marketing manager, Coenraad Groenewald, the culverts are some of the largest seen in South Africa and the contract to supply them could well be the country’s biggest single culvert order. Weighing 12.8 tons each, they are being produced at Aveng Manufacturing Infraset’s Brakpan manufacturing facility.
This is the first time that DRA has used precast concrete culverts for coal stockpiling tunnels. Steel and in-situ concrete were also considered, but DRA project engineer, Arthur Oosthuizen, said recent durability and maintenance concerns with steel tunnels and time constraints with in-situ concrete construction prompted the decision to opt for precast concrete.
“The culverts comprised of solid steel-reinforced concrete and are designed to handle well in excess of the maximum 20 ton loading they are likely to encounter at Tweefontein,” says Groenewald. “Each culvert contains 600kg of reinforced steel and measures 3.5m (height) x 5.3m (width) x 1m (depth). The walls are tapered, with a maximum thickness of 350mm at the top end narrowing to 300mm at the base of each foot.”
Initially the requirement was for a height of 4.7m but this would have rendered the culverts too large for transportation by road. To make up the required elevation, the foundations have been built with raised uprights measuring 500mm.
Mining equipment, bought for R1.5-billion, includes a large 1570 Bucyrus dragline, which will move huge volumes of material at optimal efficiency in the large pits.
The truck-and-shovel mining method, which has already been deployed in the first two pits, is earmarked for use in the smaller pits.
The productivity of mining equipment is measured across the Glencore group monthly, taking in the company’s coal operations in Australia, Colombia and South Africa. Output is measured in bank cubic metres (bcm) against the nameplate capacity of the equipment used.
The target for the dragline is to achieve 2 000 bcm an hour, while the target for the bigger shovels is 1 100 bcm an hour and 750 bcm an hour for the smaller shovels.
Caterpillar supplied most of the rubber-tyred mobile equipment and dozers and Hitachi the excavators and backhoes.
Topsoil fleets are made up of 85 t excavators and 40 t articulated dump trucks and the primary loading fleet is made up of 260 tons backactors, 350 tons face shovels and a 200 ton class front-end loader.
The development has delivered a low-cost, long-life brownfield expansion that has elevated TOP into a modern, predominantly opencast operation that mines the rich pillar reserves that were left behind in discontinued underground workings.