Parametric Analysis Applied to the Geometric Optimization of Filtered Iron Ore Tailings Stacks

Kevyn Dias Silva, Michel Melo Oliveira, Eduardo José Diniz

The high iron ore output in Brazil and the regulatory restrictions imposed on tailings dams
after the Mariana (2015) and Brumadinho (2019) failures have accelerated the adoption
of dry stacking of dewatered tailings. This work develops a parametric analysis for the
geometric optimization of filtered iron ore tailings stacks, assessing the influence of slope
angle, berm width and bench height on the factor of safety (FS) and the storable volume,
in accordance with ABNT NBR 13028-3:2025. Three-dimensional modeling and volume
estimation were performed in Micromine, and stability analyses in Slide2, using the
Morgenstern-Price limit equilibrium method under drained conditions with effective-
stress parameters. The study was carried out in two stages: Stage I used reference
parameters compiled from the literature for filtered and compacted tailings from the Iron
Quadrangle (φ' = 33°, c' = 0 kPa, γ = 22 kN/m³), and Stage II applied the methodology to
the topography and laboratory parameters of an actual operation (φ' = 32°, c' = 0 kPa, γ =
19.8 kN/m³). Results show that the slope angle is the governing geometric parameter for
FS, with limiting angles of 23° (Stage I) and 24° (Stage II) for the FS ≥ 1.50 criterion;
berm width has no measurable effect on global stability (FS coefficient of variation below
1.1%), acting only to reduce volume; and bench height yields an FS that converges
asymptotically to the value governed by the individual slope inclination beyond a
threshold (H ≈ 6.5 m in Stage I). It is concluded that geometric design should fix the slope
angle at the regulatory limit and optimize berm width and bench height solely as a
function of storable volume.