Quantifying The Cost Of Dilution In Underground Mines

Approximately 51 % of all ore production in Canadian underground metal mines is derived directly from open-stope operations. This method requires that large excavations remain open until the ore is extracted with a minimum acceptable level of dilution. A survey of underground mines in 1988 reported that a major factor in their closure was uncontrolled dilution. It has been reported that 40% of openstope operations were experiencing dilution in excess of 20%. This level of dilution has significant implications on the economic viability of a project, especially when one considers that a rate of return on a positive project is generally between 10% and 20%. This paper reports on the various definitions of dilution, on the methods of stope design that are presently used with the objective of reducing dilution and on a recently available survey technique that enables dilution to be quantified.