豪州・Ｎｏｒｔｈｐａｒｋｅｓ鉱山Ｅ４８鉱体に見るブロックケービング技術

Abstract

Block caving is a most cost effective underground mining method and it is expected as a major mining method in the near future by replacing large-scale/massive open pits where a risk of slope failure and waste/ore ratio is higher as pit depth is deeper. The Northparkes Mines is well known as a pioneer of block caving mining in Australia and has ever produced copper-gold ore by using block caving from 1995. The E48 mine is the fourth block caving project in the mines and its development was started in 2006 following the block cave production in the E26 mine. The ore body can be categorised as a porphyry copper-gold deposit and the geometry is almost shaped pipe. The extraction level is located about 600m below the surface and its footprint is sized only 310m x 193m in plan, which means the E48 has very 'tall' mining zone comparing to other block caving projects in the world. The cavability has been assessed by intensive geotechnical studies based on the past experiences in the E26 mine. The extraction level is designed to maximise not only mining recovery but also productivity, taking into account stability of all the drives. Post-undercut method was selected to initiate caving and designed carefully not to damage the extraction level excessively by stress concentration and blasting. In order to improve safety, work environment, productivity and mining cost, all underground electric loaders are unmanned and to be operated remotely from the surface office by only a couple of operators.