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Ultra-fine cemented backfill (UCB) materials display distinctive rheological characteristics. This paper examines the rheological behaviors of UCB composited with cement and tailings that have a 80% cumulative passing size (d (80) ) of 9.72 µm. The findings were that UCB samples exhibit time-dependent non-Newtonian behaviors with a shear thinning characteristic, and both thixotropy and rheopexy properties are observed under long periods of steady-state shearing (300 s −1 shear rate). The results indicate that samples sheared at higher rates display lower apparent viscosities compared to the samples sheared at lower rates. At low shear rates (≤0.5 s −1 ), apparent viscosity increased until it reached a local peak (or two peaks) before behaving similarly to samples tested at higher shear rates. It was also found that the apparent viscosity of UCB increased consistently as the solids content was increased. Moreover, as cement content was increased, the apparent viscosity rose until it reached a peak at a cement content of 6%. The results also confirmed effects of solids concentration profiles changing over time and the cement hydration on the rheological behavior of UCB. [ABSTRACT FROM AUTHOR]

• A image-based method is proposed to estimate the 3D Wadell roundness of particle. • An alternative strategy to estimate roundness from other shape descriptors is tried. • The image-based roundness estimation method is suitable for various shapes. Wadell roundness is a general particle shape descriptor used in many fields, such as mining engineering, civil engineering, and geotechnical engineering. Initially, Wadell roundness was defined as two-dimensional, and now it has been generalized to three-dimensional. This study proposes a novel image-based method using topographic analysis to estimate the three-dimensional Wadell roundness of irregular particles. And an alternative strategy to estimate 3D Wadell roundness from other shape descriptors is further proposed. The effect of mesh density on 3D Wadell roundness is quantitatively analyzed. In addition, the relationships between 3D Wadell roundness and eleven shape descriptors, including 2D Wadell roundness and the other ten 1D, 2D, and 3D shape descriptors, are discussed. Finally, the computation time of the 3D Wadell roundness estimation algorithm proposed in this study is recorded to evaluate the algorithm's efficiency. The results show that the 3D Wadell roundness estimation algorithm is robust and can be used for idealized geometries and realistic particles of various shapes. The mesh density of particles significantly influences the 3D Wadell roundness. It proved difficult to predict the 3D Wadell roundness from the eleven shape descriptors mentioned in this study. The 3D Wadell roundness estimation algorithm can be finished in a few minutes, potentially using the algorithm in rock shape analysis and mechanics responses investigation. [ABSTRACT FROM AUTHOR]