Iron ore tailings upstream dam closure and subsequent dry stacking: stiffness assessment

Brazilian novel legislation requires the closure of upstream heightened tailings storage facilities by decommissioning to minimize the risks associated with tailings storage and management. Nevertheless, such procedures demand the removal and reallocation of a significant volume of tailings that must be adequately treated and characterized to provide the necessary information for its upcoming use. An option is the tailings dewatering for pilling up in stacks. Therefore, the present research’s main goal was to evaluate the small-strain stiffness (G_max) of four samples of iron ore tailings retrieved from distinct locations of a dam that was about to be decommissioned. The materials were compacted at two relative density values (D_r = 20% – loose and D_r = 100% – dense) and submitted to triaxial tests in which G_max was measured (in stages) during the consolidation phase using bender elements. In addition, resonant column tests were also performed at a single confining pressure. The results have shown that by adopting a proper void ratio function f(e), the G_max data can be expressed by the same power-type relationship, considering the same tailings material. It was also demonstrated that f(e) depends on the material’s gradation and mineralogy and can be expressed as a function of some particle shape parameters.