Modelling particle sedimentation in cemented paste backfill pipe flow using cohesion-enhanced granular kinetic theory

Cemented paste backfill (CPB) is widely used in underground mining for ground stabilisation and tailings management. During pipeline transport, its high solid concentration, yield-stress-dominated rheology and interparticle cohesion can produce complex flow resistance and non-uniform phase distribution. Eulerian multiphase models distinguish the solid and liquid phases but generally neglect interparticle cohesion, limiting their ability to describe cohesion-induced yield behaviour. To address this gap, this study aims to develop a CPB-oriented cohesion-enhanced Eulerian-kinetic theory of granular flow (KTGF) framework capable of linking the cohesion-induced rheological behaviour with solid-phase redistribution during pipeline transport. Specifically, this study further improves an existing cohesion-enhanced granular Eulerian multiphase model by refining its cohesive interaction treatment and concentration-dependent structural function. Hydration-related bonding and van der Waals forces are incorporated to represent interparticle cohesion, while the concentration-dependent structural function is modified to describe the strong rheological stiffening of CPB at high solid fractions. The model is evaluated against experimental slump and pipeline pressure-flow data. The modified model achieves mean relative errors of 10.8%, 8.6% and 3.9% at solid mass concentrations of 71.7%, 73.1% and 75.3%, respectively, whereas the standard non-cohesive KTGF model shows errors ranging from 26% to 73%. Simulation results reveal that increasing flow velocity reduces particle enrichment near the pipe invert, while increasing solid concentration and cohesive strength promotes a more uniform phase distribution. Larger pipe diameters enhance phase redistribution due to the reduced average shear rate. The results also demonstrate the importance of explicitly incorporating cohesion to link CPB rheology, particle motion and flow resistance, and provide practical guidance for pipeline design, operating-velocity selection and deposition-risk assessment.