Field and laboratory study of compacted filtered iron ore tailings-Portland cement blends for dry stacking purposes

The dry stacking of filtered tailings emerges as an alternative to deal 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. Also, the cement addition provides further challenges to the design of these structures. Thus, obtaining reliable laboratory data for properly designing these tailings storage facilities is essential. Accordingly, this paper evaluates the mechanical behaviour of artificially cemented iron ore tailings for dry stacking purposes, focusing on comparing the responses between on-field compacted samples and laboratory-assembled specimens. For such, the following tests were carried out: ultrasonic pulse velocity, unconfined compression, split tensile, and triaxial compression. Both the stiffness and the strength data could be well-described by the porosity/cement index, and, despite minor differences, there was a good agreement between the responses of laboratory and field compacted samples. These findings highlight the laboratory procedures’ adequacy in reflecting the material's real on-field conditions.