Behavior of mine tailings under cyclic hydraulic loading

Abstract

Shallow water cover is one of the most effective methods of managing sulfide-bearing reactive mine tailings. Unless sufficient water cover depth is provided, surface erosion by wind-induced waves and pressure-driven currents can re-suspend the tailings and expose them to dissolved oxygen and affect the quality of the water cover. The present study gives a simple approach for the estimation of the critical shear stress for surface erosion of mine tailings and cohesive sediments under shallow water cover. Erosion tests were carried out in a Plexiglas laboratory annular column on mine tailings and sediments under a 50 cm water cover. The annular column was 30 cm in diameter, 120 cm in height and had a 9 cm annular flow width. Shear stress was introduced through a motor driven Teflon stirrer to investigate the initiation of motion and subsequent re-suspension of newly deposited mine tailings and sediments. The velocity field and the pressure change in the boundary layer were measured by laser Doppler velocimeter (LDV) and Preston tube, respectively. The ranges of critical shear stress for the tailings and sediments were estimated by the LDV and Preston tube measurements and visual observation. The results showed that the erosion behavior of most of the mine tailings can be explained by a power law erosion equation.