Influence of Stress State on the Expected Behavior of Filtered Iron Ore Tailings for Compacted Stacking Disposal

An experimental study was conducted to analyze the geomechanical behavior of filtered iron ore tailings over a range of densities, confining pressures, and stress paths. Because of the recent developments of filtered tailings stacking in Brazil, studies on the properties and behavior of these materials have become relevant. Two nonplastic silty sand tailings with different fines content were investigated. Samples were reconstituted, simulating loose and dense conditions under confining pressures ranging from 200 up to 1,600 kPa. The critical state lines (CSL) of the tailings are curved in the e - log p^′ plane, with a flat trend at low mean effective stress, indicating the instability of these materials in looser conditions. As the confining stress increased, there was a reduction in strain-softening response, and CSL became steeper and parallel to the respective consolidation line. For the tested confining pressures, although marginal, indications of grain breakage were observed, especially for the coarser tailings. This suggests that the steeper slope of CSL at higher mean effective stresses is associated with the particles’ morphological evolution (shape and surface roughness) and particle breakage. The K₀-consolidated tests showed minor significance in the CSL definition, as they were unable to attain the frictional behavior even after undergoing a 20 % axial strain, unlike the instability line, which is strongly influenced by induced anisotropy.