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

Abstract

Understanding the geotechnical properties of iron ore tailings is one of the biggest challenges currently faced by the mining industry. 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. The results and analysis of a laboratory programme aimed at assessing the small-strain stiffness of tailings materials are presented in this paper. The materials tested 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 with different grain size distributions were used – flotation tailings, slimes tailings and blended tailings. Reconstituted specimens were prepared at different densities (loose and dense conditions) to assess the effects of initial density (percentage compaction) on the shear modulus. The laboratory results were compared with empirical correlations for other soil types. The equations were ineffective at representing tailings materials containing large amounts of fines (slimes). The advantages and limitations of the equations are discussed and a new empirical equation that includes the degree of compaction is suggested.