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The dry stacking of filtered tailings has emerged as an alternative way of dealing with the safety-related problems of conventional slurry disposal in reservoirs behind upstream dams. Incorporating a cementing agent into the tailings before compaction can enhance the overall geomechanical behaviour of these structures, giving rise to more stable and safer stackings. However, few dry stacks are in operation worldwide and their field performance needs to be better understood. In addition, the addition of cement provides further challenges to the design of these structures. Obtaining reliable laboratory data for properly designing these tailings storage facilities is thus essential. Accordingly, the mechanical behaviour of artificially cemented iron ore tailings for dry stacking purposes was evaluated, with a focus on comparing the responses between field-compacted samples and laboratory-assembled specimens. To do this, ultrasonic pulse velocity, unconfined compression, split tensile and triaxial compression tests were carried out. Both the stiffness and strength data were well described by the porosity/cement index and, despite minor differences, good agreement was found between the responses of the laboratory-assembled and field-compacted samples. The findings highlight the adequacy of laboratory procedures for reflecting the material's real-field conditions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]