Research on flowing resistance and pressure monitoring in conveying pipeline of paste filling slurry with composite aggregate

Maoping Lead-Zinc Mine utilizes composite aggregates of tailings and manufactured sand for paste filling. The filling pipeline system features a vertical drop exceeding 600 m and horizontal pipelines over 5 000 m in length, belonging to the category of high vertical drop and long-distance paste filling. Maintaining the stable transport of paste slurry is vital for mine backfill operation. To address frequent pipeline blockages and bursts and improve the filling borehole full-pipe ratio and transport stability, the physical parameters of tailings and manufactured sand and the rheological parameters of paste slurry using tailings and manufactured sand as composite aggregate are obtained through test. Based on the rheological parameters of composite aggregate paste slurry, the specific frictional resistance of filling slurry conveying in pipeline is calculated, and the analytical formula of slurry height in borehole is deduced by Bernoulli equation. Furthermore, pressure monitoring devices are installed in the horizontal filling pipeline in the 610 m level in Hedong Mine Area of Maoping Lead-Zinc Mine and a study on the pressure monitoring in conveying pipeline of paste filling slurry with composite aggregate is carried out. The results show that when the filling slurry is in laminar flow or transitional flow, the specific friction resistance calculation formula obtained by Buckingham formula has high accuracy. When the filling flow quantity is 60 m³/h and the filling slurry with cement-sand ratio of 1∶4 and mass concentration of 76%, the specific friction resistance of filling slurry is 5 392 Pa/m. When stowing gradient is less than 2, the full pipe rate of the borehole is less than 50%. In the backfilling engineering practice, the full pipe rate can be improved by optimizing pipeline layout to increase stowing gradient, increasing filling quantity and mass concentration of slurry, and reducing pipe diameter to increase specific frictional resistance and increasing local resistance loss. This study offers valuable references for parameter design and stability optimization of backfilling systems in similar domestic mines.