Determination of critical state line (CSL) for silty-sandy iron ore tailings subjected to low-high confining pressures

Abstract

The disposal of filtered tailings in high dry stacks can induce particle breakage, changing the material's behaviour during the structure's lifetime. The grading changes influence material properties at the critical state, and this is not mature for intermediate artificial soils (tailings) in a broad range of confining pressures. In this paper, it aims to describe the behaviour of iron ore tailings in a spectrum of confining pressures broader than the reported in previous studies. A series of consolidated drained (CD) triaxial tests was carried out with confining pressures ranging from 0.075 MPa to 120 MPa. These results show that the amount of breakage plays an essential role in the response of iron ore tailings. The existence of curved critical state line (CSL) in both specific volume (ν)–logarithm of mean effective stress (p′) and deviatoric stress (q)–mean effective stress (p′) planes, and different responses in the deviatoric stress–axial strain–volumetric strain curves were verified. An inverse S-shaped equation was proposed to represent the silty-sandy tailings' behaviour up to high pressures on ν–lnp′ plane. The proposed equation provides a basis for enhancing constitutive models and considers the evolution of the grading up to severe loading conditions. The adjustment considered three regions with different responses associated with particle breakage at different pressure levels.