Pore Structure Characterization of Tailing Bed and Dewatering Mechanism at nm-µm Scales Under Shearing

The preparation of high-density tailings is a prerequisite for cemented paste backfill technology, and the flocculated fine tailings of sealed water leads to challenges in the slurry thickening of tailings. Shearing conditions can compact the micro floc structure to improve the underflow concentration. The nm-μm scales of pore characteristics and connectivity are essential for the dewatering process. The computed tomography (CT) results show that the underflow concentration increases from 62.3 wt% to 68.6 wt% after undergoing rake shearing at 2 rpm, and the porosity decreases from 42.7% to 35.54%. The shearing conditions reduces the spheres and sticks by 43.14% and 43.3%, respectively, from the pore network model (PNM). The seepage flow states were affected by the changes in the pore structure. The maximum surface velocity and the maximum internal pressure decrease after undergoing shearing. Shearing conditions can break the micro floc structures, and the fine particles can fill in the micron-scale pores by gravity and shearing conditions, resulting in the forced drainage of water into the pores. Shearing conditions can break the thickening floc network structures; natural fine particles can fill the micron-scale pores by gravity and shearing conditions. The upward seepage of sealed water along the μm-scale pore channel causes a higher bed concentration. However, the sealed water in the nm-scale pores cannot flow upward due to water cohesion and particle adhesion resistance.