One of the deepest backfill operations in the world is to be upgraded to accommodate advanced mining methods at Gold Fields’ South Deep gold mine.

South Deep, a fully mechanised deep level mine, will be equipped with a new backfilling plant using innovative technology to de-stress the mining areas and backfill the complete economical reef package with a width and height of more than 15m.

Improved backfilling technology

"The advantage of backfill is that all voids in the mining areas are filled with a suitable product to supply regional support, resulting in a much safer operational mine as well as a higher extraction rate," says Rob Bradley, manager of mine engineering at Murray & Roberts Cementation.

Filling has been designed as a continuous process and will terminate at a depth of 2,800m. "It is anticipated that 330,000t of ore will be mined per month," says Warwick Luke, engineer at Murray & Roberts Cementation. "To backfill effectively, the plant was designed with a capacity of 140,000m³ per month and for full plant tailings due to the size of the stopes and drainage considerations."

Improved technology incorporated in the design includes the use of a deep cone thickener, which is considered a more cost effective option and requires less maintenance.

The working system of the new plant

Tailings are pumped from the gold plant to a storage facility and then to the deep cone thickener where binder is added to the thickened material. The backfill slurry is gravity fed underground via the surface main shaft and then the sub vertical shaft to the levels where it is required.

De-stress stopes are backfilled prior to the longhole drilled stopes, which will be 15m in height and width and up to 60m long. The material is fed through thick walled steel piping under-gravity to reach all the backfill areas.

Operation to start in 2010

Murray & Roberts Cementation has conducted a feasibility study prior to the start of detailed engineering. The system is designed for construction in a modular form and it will allow the mine to expand the backfill plant as more capacity is required.

The first module for the new plant at South Deep is scheduled to go into operation in late 2010, with a second module due to be completed over the next three years.

Murray & Roberts Cementation has been involved in backfilling projects since 1981 and has gained extensive experience in tailoring packages to suit each individual project.