Experimental investigation of solid-liquid two-phase flow in cemented rock-tailings backfill using Electrical Resistance Tomography

The cemented rock-tailings backfill (CRB) technique is a rapidly advancing technique for the mine backfill process. However, the inclusion of waste rocks in backfill materials increase the transportation burden on the backfill pipeline. In particular, it can accelerate pipeline wear and significantly increases the probability of the backfill pipeline being blocked by large waste rocks. To ensure safe transportation, we proposed a visual detection method for liquid-solid two-phase flow inside a backfill pipeline based on Electrical Resistance Tomography (ERT). In particular, we established a finite element model (FEM) for the 16-electrode ERT sensor to study in detail the detection sensitivity of the ERT 'soft field' effect. Using orthogonal experiments, we also analyzed the effects of the solid concentration, particle size, and waste rock-to-tailing ratio on the electrical conductivity of the backfill slurry. According to the experiment results, we simulated the positions of waste rocks in the pipeline. A linear back-projection algorithm was utilized to perform the inversion imaging of the 9 sets of flow patterns in the orthogonal experiments. The research results indicate that the most important factor affecting the conductivity of backfill slurry is the ratio of waste rock to tailings. The conductivity of the backfill slurry reached a maximum of 3.8 mS/cm for a solids concentration of 50 wt%, particle size of 25-50 mm, and waste rock-to-tailing ratio of 70/30. We found that waste rocks in the backfill pipelines could be accurately located using reconstructed images. Finally, we conclude that, with an imaging time of only 0.04 s, ERT analysis has the potential to fully meet the real-time requirement of online monitoring of the backfill slurry transportation.