Abstract
In recent years, stoping methods have been magnified as an extraction strategy in underground hard rock mining. According to a report from Austrade (2013), in 2013 70% of underground metal mines in Australia utilized open stoping, sublevel stoping, various narrow stoping methods, and other types of stoping and caving methods to extract ore. In addition, 51% of underground metal production in Canada relies on open stoping methods (Pakalnis et al., 1996). A disadvantage of popular stoping methods is that many mines are severely affected by dilution problems. Pakalnis (1986) surveyed 15 open stope Canadian mines and concluded that 47% of the operations suffered from more than 20% dilution. Likewise, Henning and Mitri (2007) reported that approximately 40% of open stoping operations in Canada suffered from 10% to 20% dilution. Dilution can be defined as ‘the contamination of ore with lower grade material’, and it can be generally classified into two categories: planned and unplanned. Planned dilution, also referred to as primary or internal dilution, is contamination by low-grade material within the ore block; whereas unplanned dilution, also known as secondary or external dilution, is contamination by lower grade material exterior to the ore block. Both of these dilute the ore stream value. Ore loss can similarly be classified as planned and unplanned. Planned ore loss represents the ore-grade material that has been excluded from the mining block at the stope design stage, whereas unplanned ore loss is the part of the mining block that remains in the stopes after mining. This study includes unplanned dilution and ore loss, which can be attributed to as overand underbreak in underground stoping production. These phenomena can be divided into dynamic and quasi-static types; the quasistatic type occurs after blasting, while the dynamic type occurs immediately (Mandal and Singh, 2009). The dynamic overand underbreak types are the main interest of this study, and a new terminology, ‘uneven break’ (UB), is used to identify it. To extend the definition of dilution, UB can be defined as the tons of mined unplanned dilution (positive) or ore loss (negative) per ton of ore mined, expressed as a percentage.
Highlights
In recent years, stoping methods have been magnified as an extraction strategy in underground hard rock mining
Multiple linear regression analysis (MLRA), Multiple nonlinear regression analysis (MNRA), and artificial neural network (ANN) were used to develop the optimum UB prediction model based on 1067 data-sets with ten UB causative factors from three longhole stoping underground mines in Western Australia
The MLRA, MNRA, and ANN prediction performances were compared with the current prediction mine results (Figure 5)
Summary
In recent years, stoping methods have been magnified as an extraction strategy in underground hard rock mining. This study includes unplanned dilution and ore loss, which can be attributed to as over- and underbreak in underground stoping production. These phenomena can be divided into dynamic and quasi-static types; the quasistatic type occurs after blasting, while the dynamic type occurs immediately (Mandal and Singh, 2009). UB affects the safety of the workforce and machinery, but is severely detrimental to the viability of the operation throughout all of the mining stages It directly downgrades the ore and causes unnecessary mucking, haulage, crushing, hoisting, and milling activities, decreasing productivity.
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