Influence of compaction on small-strain shear modulus of iron ore tailings

Understanding the geotechnical properties of iron ore tailings is one of the biggest challenges that the mining industry currently faces. The brittle behaviour of these tailings has brought the importance of small strain stiffness to the geotechnical forefront. However, lack of knowledge and information about the behaviour of iron ore tailings still exists. This paper presents the results and analysis of a laboratory program that aimed to assess the small strain stiffness of tailings materials. These materials were produced during the iron ore treatment process. Bender elements were used to measure shear wave velocities and evaluate dynamic shear moduli at different effective stress levels resulting from isotropic consolidation tests. Three types of iron ore tailings were used: (1) flotation, (2) slimes, and (3) blended with different grain-size distributions. Reconstituted specimens were prepared at different densities (loose and dense conditions) to assess initial density effects (percent compaction) upon the shear modulus. The laboratory results were compared with empirical correlations with other soil types. Nevertheless, these equations were ineffective in representing tailings materials that contain large amounts of fines (slimes). The advantages and limitations of these equations are discussed, and a new empirical equation that includes the degree of compaction is suggested.