Development of a suitable mine backfill material using mine waste for safe and economic ore production at Konkola mine(Zambia)

The use of backfill in underground mines has increasingly become an integral part of overall mining operations all over the world. This has largely been driven by the need to increase ore recovery and productivity. The underground mining activities have given rise to creation of large volumes of voids which, if not addressed, would lead to long term global instability of the mine. The ever-increasing depths reached by underground mining will, in the future, place even more demands on sound backfill and mine design systems if safe and efficient operating conditions are to be maintained. Environmental protection and increasing need for economic use of surface land have demanded use of underground waste as backfill material.

Geotechnical investigations have been carried out on the available mine waste materials at Konkola Copper Mine (KCM) in Chililabombwe, Zambia, to develop a suitable backfill material for safe and economic ore production at Konkola mine (Zambia). The material would need to have the strength of 1 MPa, as spelt out by Konkola mine management and suitable drainage characteristics to resist failure due to self weight in a backfilled stope and therefore facilitate ore pillar recovery.

Geotechnical tests have shown that the suitable backfill material for safe and economic ore production at Konkola Mine is the blend between the hydraulic fill material produced at 65% solid fraction at the old backfill plant and waste rock from No.3 Shaft Dump crushed to 2.83mm size. The blend ratio must be 3:7 by weight, respectively, with the addition of 4% Zambezi Portland cement. This material, mixed on surface, must be pumped to the various stopes underground at Konkola Mine and allowed to cure for not less than 28 days to attain the recommended UCS of 1 MPa needed to facilitate total ore pillar recovery.