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

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.