Bivariate rheological model of ultrafine tailings backfill slurry based on structural parameter and its applications

Ultrafine tailings have become the largest solid waste in metal mine filling treatment. The rheological model provides a theoretical foundation for capturing its flow characteristics and determining the pipeline transportation parameters. To describe the shear response process of ultrafine tailings slurry, firstly, the concept of the structural parameter in this paper was introduced based on the formation mechanism of ultrafine particle flocculation structure. Then, a rotary viscometer was used to conduct 24 groups of rheological tests on the ultrafine tailings slurry with mass fractions of 72%, 74% and 76% and cement contents of 240 and 260 kg/m³under different shear strengths. The results show that under constant shear strength, the shear stress of the slurry gradually decreases with the increase of shear time, and ultimately tends to be stable; under any shear time, the shear stress and shear rate (>20 s-1) approximately satisfy the Bingham model, and the Bingham regression parameters are obviously time-varying. The reason for these macroscopic laws can be attributed to the change of the slurry structural parameters. According to these evidences, a bivariate rheological model of the ultrafine tailings slurry with respect to shear strength and shear time was proposed, in which seven parameters have certain physical meanings. The proposed model was verified by the experimental data, and the rheological parameters of the ultrafine tailings slurry with the given mix are obtained by the best fitting. The maximum yield stress and maximum plastic viscosity range from 120 Pa to 220 Pa and from 1.7 Pa•s to 7.2 Pa•s, respectively, which can provide a reference for the calculation of the starting pressure; the range of the limit yield stress and plastic viscosity are from 20 Pa to 120 Pa and from 0.5 Pa•s to 3.2 Pa•s, respectively, which can give a reference for the calculation of the steady-state flow resistance of the slurry. Lastly, the applicable conditions and methods of the proposed rheological model are discussed, and also compared with the existing rheological model. The research results can provide theoretical and experimental basis for mine filling design. © 2021, Science Press. All right reserved.