The pore structure and permeability evolution of thickened fine grained tailings during deposition consolidation

Thickened tailings differ significantly from low-concentration tailings in deposition and consolidation patterns due to their higher solid mass concentration. A systematic investigation of the deposition, consolidation behaviors, and permeability of thickened fine-grained tailings is essential to address potential discrepancies in the storage processes of tailings. This study investigates the self-weight deposition and consolidation processes of various thickened tailings through deposition column tests, indicating the governing laws of deposition and consolidation. Tailings pores are classified into ultrafine pores, micropores, minipores, mesopores, and macropores based on standard pore size classifications. In addition, the microporous structures and permeability characteristics of the tailings under varying consolidation stresses are examined using nuclear magnetic resonance (NMR) non-destructive testing and a consolidation permeability test system. The results showed that thickened tailings predominantly undergo consolidation settlement. As consolidation stress increases, the pore structure becomes compacted, and over 97 % of the pores are classified as ultrafine or micropores in fine tailings. Although these tailings exhibit high porosity, their limited permeability is attributed to the weak contribution of ultrafine pores and micropores to fluid seepage. A quantitative model correlating the T₂ spectral area of pores larger than 0.1 μm with the permeability coefficient is developed, offering insights into the permeability of tailings under different stress conditions. This study provides insights into the permeability development of fine tailings under consolidation.