Rainfall infiltration-induced vertical differentiation of pore structure and permeability in mine tailings: a throat-dominated mechanism

Seepage-induced particle migration in tailings alters pore structures, risking dam stability. This study quantitatively assesses vertical pore structure differentiation during sustained rainfall infiltration using micro-CT and pore network modelling (PNM). Results show that total porosity varies by 5%, while connected porosity declines by nearly 20%. Surface layers develop high-connectivity networks via throat expansion, while deep-layer networks degrade due to pore isolation and particle depletion. PNM simulations validate that throat radius governs permeability evolution, showing significantly higher sensitivity than pore radius, consistent with Hagen-Poiseuille law. This reveals heterogeneous permeability distributions, indicating that characterising pore network topology is essential for understanding tailings seepage behaviour.