Mining Magazine > Panorama > South Deep FPT backfill plant near completion

Murray & Roberts Cementation is close to completing the construction of a cemented full plant tailings (FPT) backfill plant at Gold Fields’ South Deep gold mine near Westonaria, South Africa. The commissioning of phase one of the new plant — the largest of its kind in South Africa — will represent the third type of backfilling implemented at the mine over a period of 18 years.

Rob Bradley, manager mine engineering at Murray & Roberts Cementation, said that the application of backfilling has passed through three stages owing to the various mining methods which have been used during the development of the mine to date. These methods have required the adaption of the backfill type and system to keep pace with production levels and geological structures. The three stages comprise the backfilling of the new twin shaft pillar area, followed by cyclone classified tailings backfill (hydraulic fill) for the narrow tabular stopes, as well as some larger stopes, and finally, de-stress and long-hole mining backfill to suit present day requirements.

Mr Bradley added: “Each change was preceded by significant feasibility studies and test work to mitigate all safety risks and ensure a robust and cost-effective solution. A depth of 3200m below surface, as well as the size of the orebody, has made the South Deep backfill project one of the most challenging and exciting undertakings we have ever been involved in.”

The entire FPT system — designed and engineered by Murray & Roberts Cementation — is expected to be fully functional by July 2012.

Tailings will be transferred from the gold plant to be temporarily stored in four storage tanks, previously used in the gold leaching process, and will either be pumped back to the gold plant or to the backfill plant, depending on the backfill requirement.

Mr Bradley said: The design of the FPT plant makes provision for all gold plant tailings to be supplied to the new backfill plant for FPT backfill manufacturing, with a provision for excess tailings to be transferred back to the gold plant for disposal on the tailings dam, should the backfill plant be unavailable. The backfill plant will require a constant supply of gold tailings at a rate of 420t/h, with relative density of 1.4 to manufacture 148,000m³ FPT backfill every month.”

The backfill plant will be equipped with flushing facilities to prevent binder, tailings and backfill lines from being blocked. Flushing water for the plant will report to the backfill plant sump before it is pumped back to the gold plant. A standby generator will provide power for essential operations to continue in the event of a power failure, but will not operate the entire plant.

Mr Bradley said that a total of 24 pipes have been allowed for the final reticulation. Nominally, only 12 pipes would be required to supply the quantity of backfill, but owing to the vast geographical area and the mining sequence, it was necessary to spread the backfill reticulation over large areas.