Effect of particle size distribution of tailings on pressure gradient and drag reduction characteristics of non-cemented paste considering wall slip

The paste slurry exhibits pipe wall slip characteristics during transportation, thereby effectively reducing pipeline transportation resistance. In order to study the characteristics of paste pipeline transportation with wall slip characteristics, a pipeline pressure gradient model considering wall slip effect was applied. In order to verify the accuracy of the model, the overflow tailings and classified tailings of a lead-zinc mine were taken as the research object. According to the two-dimensional compaction theory, the mixing ratio of overflow tailings was determined to be 8% ∼ 39%, and five kinds of tailings with different gradations were configured accordingly. The loop test, rheological test and settlement test were carried out. Taking the rheological parameters, limit volume concentration and average particle size as the basic parameters, the pressure gradient value considering the wall slip effect is obtained and compared with the measured pressure gradient of the loop test. The results show that the relative error between the model prediction results and the measured values is 10%, which has high reliability. The pressure gradient and mass concentration show a quadratic function growth trend, and have a linear relationship with the pipeline flow rate. With the increase of the proportion of －38 µm particles, the pressure gradient shows a secondary growth trend. With the increase of the proportion of + 38 µm particles, the pressure gradient shows a quadratic function decreasing trend; The slip drag reduction rate gradually decreases with the increase of mass concentration, and is not affected by the flow rate of the pipeline. When the proportion of －38 µm particle size is 27.43% ∼ 38.32%, the slip reduction rate is more significant. Considering the actual project and transportation cost, the corresponding overflow tailings incorporation ratio is 16% ∼ 31%.