Rheological properties of tailings paste based on a spread test

Paste backfill is similar to surface paste disposition. Paste backfill technology is an innovative method of treating tailings, which is carried out beneath the earth. This process is widely used worldwide in many metal mining industries due to its advantages in safety, environmental protection, and high economic benefit. The rheological properties of paste backfill are essential factors in pipeline design. After analyzing paste backfilling practices for a long time, it is concluded that the slump determined according to concrete standards is not suitable for paste backfill of tailings. To increase the efficiency of the process, a spread parameter was introduced in the cement slurry flow test method to investigate the rheological properties of the paste backfill. Experiments were conducted to analyze the relationship between spread and other factors such as mass fraction (C_w) of paste backfill, cement-tailings ratio, yield stress, and viscosity. Based on the test results of spread and rheological parameters of paste backfill of tailings in five mines, the empirical model representing spread and yield stress of paste backfill of tailings was constructed and compared with the deduced analytical model. The results show that the spread of paste backfill is mainly related to mass fraction, and the effect of cement-tailings ratio on it is small. The spread of paste backfill decreases with the increase in mass fraction, yield stress, and viscosity. The spread of paste backfill of tailings with mass fraction of 68%, 70% and 72% are 20.37, 17.22 and 12.44 cm, respectively. Spread of paste backfill has an exponential relationship with its yield stress. The error between the yield stress calculated using empirical model and the actual test is within 25%, and decreases with the increase in mass fraction of paste backfill, which will be within 10%. The yield stress calculated using analytical model and empirical model are more or less the same when the spread of paste backfill of tailings is between 12 cm and 16 cm. The calculated yield stresses of analytical model are generally higher than actual test values. Compared with the slump, the spread test is simple and easy to operate, which can adequately characterize the rheological properties of paste backfill of tailings and guide in-situ backfilling.