Quantitative analysis of static yield stress variation in thickened tailings in compaction zone based on fine structure

The poor flowability of the high-concentration tailings slurry is likely to cause slurry hardening and rake blockage of the thickener. Therefore, the effect of slurry concentration on the static yield stress (τB) of slurry was investigated and a comparative analysis of the τB of thickened tailings and freshly mixed slurry was conducted. We find that the concentration, the coarse particles content and pore structure of thickened tailings are nonhomogeneous. The slurry concentration and the coarse particles in 75-300 μm increases with decreasing slurry height, and the pore volumes in 50-250 μm are the main storage space for water. The τB of the thickened tailings is 5.3-61.3 times higher than the freshly mixed slurry, and the τB of slurry decreases with the reduction of the coefficient of variation (CV) in slurry porosity. We propose to use the CV to quantify the difference between thickened tailings and freshly mixed slurry in terms of values of τB, and it was concluded that the τB of slurry decreases with the reduction of CV in slurry porosity. The results were validated in a field application at an iron ore mine in China, likely contributes to solving the problem of slurry hardening in the silo.