Abstract
In block cave mining, rock fragmentation is a key parameter that influences the production level design and mine planning. Fragmentation occurs mainly by natural breakage during the caving process and in the draw column. The breakage that occurs within the column is known as secondary fragmentation. Secondary fragmentation has been successfully described using the block caving comminution model, which replicates the fragmentation mechanics between particles under drawn and vertical loads in a draw column. This model is based on a kinetic and population balance approach, in which non-normalized and normalized assumptions can be used depending on material and comminution system behaviour. In this paper, the non-normalized and normalized approaches are applied and compared to laboratory data to determine which assumption should be used for secondary breakage in block caving. Approaches are compared graphically, with the mean square error and the Fisher test with a false-rejection probability of 0.05. Based on a statistical analysis, the results show that the normalized model can be applied to all the rock types tested.
Highlights
The block caving method has been widely used in the mining industry for over 30 years
In cave mining, the process is influenced by the geometry of draw zones, which defines the drawpoint spacing, draw control, rate of draw, and secondary breakage (Laubscher 1994; Kurniawan and Setyoko, 2008)
The rock fragment size can cause operational problems such as hangups, oversized material, fine material migration, inrush of fines, and mudrush events. These are some of the main reasons to study and estimate the rock fragmentation in block caving mines
Summary
The block caving method has been widely used in the mining industry for over 30 years. In terms of material shape, angular particles suffer greater breakage than rounded or cubic ones of equal size and under similar levels of stress (Lee and Farhoomand, 1967; Dorador, 2016) This behaviour is explained by the load concentration in small areas of the particles, increasing the stress and facilitating fracture (Lade, Yamamuro, and Bopp, 1996). At low extraction rates, fracturing of the material depends on the effective time during which it is under stresses associated with caving and/or under arc conditions (Laubscher, 2000) Another relevant aspect in fragmentation is material transport through the ore pass. Block Caving Comminution Model Block caving is widely used in massive underground mining because of the high production rates and low operational costs With this method, rock fragmentation occurs naturally during ore extraction while caving propagates to the surface. The aim of this paper to compare the normalized and non-normalized models using statistical analysis of a variety of rock types to identify which approach should be used with block caving methods
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