Dry stacking of iron ore tailings: possible particle breakage during compaction

Abstract

Disposal of iron ore tailings (IOT) in dry stacks is increasingly common in Brazil. IOT are compacted in layers using drum rollers that cause compaction and vibration effects on the ground. Particle breakage is usually observed in granular materials when subjected to large static loads, as can occur depending on the stacking height achieved. This study investigates the breakage behaviour of IOT, simulating load conditions that may arise during compaction of the layers for dry stack construction. Two IOT samples with different amounts of clay-sized particles but similar mineralogy (about 77% quartz and 19% iron oxide – typical of IOT in Brazil) were subject to three different laboratory tests simulating cyclic, compaction and vibration loading. Particle size distribution analyses were performed before and after testing all specimens. Both IOT samples suffered only particle breakage (relative breakage between 0.12 and 0.14 for tailings A and between 0.14 and 0.16 for tailings B) under extremely high pressures (σ′v = 85 MPa) applied by oedometer testing, above those usually found in the field. For the usual pressures applied in the field, the frequency of load and number of cycles were not significant in particle breakage.