Characterization of an Iron Ore Tailing Sample and the Evaluation of Its Representativeness

The massive annual tonnage of iron ore tailings, plus the more demanding environmental policies after the catastrophic collapses of Fundão Dam in 2015 and Feijão Dam I in 2019, have forced Brazilian mining companies to search for more sustainable and safer alternatives for tailings disposal. The Brazilian mining industry has been studying the dry stacking of filtered tailings. Most companies seek the development of great dry stacks, over 200 m high, to absorb the whole tailings generation. As tailings assume a structural role, it is vital to characterize the dry stacks and understand their behaviour. This study aimed to characterize index properties, evaluate the effect of compaction on the hydraulic behaviour, and evaluate field variability of iron ore tailings from a mine in Quadrilátero Ferrífero, Brazil. Also, a database of iron ore tailings properties from Quadrilátero Ferrífero was collected and used to evaluate the results. Specimens were compacted to 93%, 95%, 97%, and 100% of Proctor’s maximum dry unit weight, and the hydraulic conductivity was defined for several confining pressures (100, 200, 400, 800, 1600 and 1900 kPa) for each degree of compaction. Index properties of the studied tailing were similar to other iron ore tailings from the Quadrilátero Ferrífero, hydraulic conductivity was proportional to the void ratio, and the field tests indicated some variability of both material properties and degree of compaction of the stacked material. The database presented in this study supplies the mining industry with a reference point for future projects.