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The mechanics of filtered compacted normally consolidated (NC) and overconsolidated (OC) iron ore tailings (IOTs) was studied by performing triaxial testing at high pressures of up to 120 MPa. The OC specimens were obtained by isotropically compressing compacted IOT to 120 MPa, unloading it to distinct confining pressures, and shearing at constant radial stress. Particle size distribution analyses were used to examine the effect of compression and shear stresses on particle breakage. Additionally, the triaxial test results illustrate the stress history influence on the deviatoric stress–axial strain–volumetric strain curves, as well as on the IOT peak strength. Furthermore, these results also show that the amount of breakage during the shearing stage plays an essential role in the geomaterial's response, marking the existence of curved critical state locus in both v–ln p′ and q–p′ planes, which is unique in the studied confined stress range (4–120 MPa) for the compacted NC and OC (considering OC ratio up to 30) IOTs. [ABSTRACT FROM AUTHOR]

Grading changes due to particle breakage are crucial in geotechnical engineering problems involving high pressures, such as elevated-height dry stacking facilities for compacted filtered iron ore tailings disposal. However, understanding the iron ore tailings response at high stress is still in its early stages in the Brazilian context. It is now marked by the increasing need for alternatives to tailings allocation rather than the traditional slurry disposal in impoundments. The present research, which examines the mechanical response of iron ore tailings and lightly cemented iron ore tailings over confining pressures ranging from 1.2 to 120 MPa for dry stacking purposes, provides significant insights into this area. The study relied on triaxial tests conducted on a high-pressure apparatus that employed specimens compacted at three different compaction degrees. The cement addition incurred slight differences in isotropic compression, enlarging the range of achievable states. Still, the shearing response of both uncemented and lightly cemented tailings was very similar, particularly at higher stress levels, resulting in an equivalent critical state locus. In the v - ln p ́ plane, an S-shaped function described the critical state and delineated the regions where particle breakage becomes an important source of volumetric strain. In brief, this study provides novel insights into the behaviour of uncemented and lightly cemented iron ore tailings in the context of elevated-height dry stacking facilities. [ABSTRACT FROM AUTHOR]

The filtered tailings disposal (dry stacking) up to 300 m high is an alternative to overcome the drawbacks related to the slurry tailings storage in large impoundments as it is safer and demands smaller portions of the existing landform. Even so, the understanding of the denser and dewatered material response over a broad range of confining pressures is essential to safely design tall dry stacking tailings facilities. Accordingly, the present research assesses the mechanical behavior of compacted iron ore tailings through triaxial tests. A series of compression and extension drained and undrained triaxial tests were conducted over a wide spectrum of confinements (σ ́ 3 ranging from 75 to 8,000 kPa) to check possible particle breakage occurrence and effects. The influence of the initial density due to compaction was, as well, evaluated since the tests were performed using specimens molded at distinct dry unit weight values. The results were analyzed in the light of the critical state soil mechanics and have indicated the existence of a curvilinear critical state line in the ν: log ṕ plane. Small particle breakage has occurred and can be associated with reduction in surface roughness, breakage of asperities, and reduction in particle angularity. Moreover, a tendency for static liquefaction was observed amongst the loosest specimens sheared under the lowest confining levels. [ABSTRACT FROM AUTHOR]