Unsaturated seepage and evaporation from a deposited mine tailings profile

Abstract

Unsaturated seepage and evaporation in a mine tailings profile was simulated using a numerical model (UNSAT 2). Three 30 cm layers were deposited at saturation on an initial profile which had a static water table 300 cm below the surface. The study focused on three variables: (1) the effect of different grain size distributions of tailings, (2) the effect of evaporation, and (3) the effect of different times between deposition of layers. Hydraulic parameters for coarse, medium and fine tailings were obtained from the literature. The fine tailings drain to residual water contents faster than the medium or coarse tailings when no evaporation is present. Evaporation affects only the near surface in the medium and coarse tailings. In the fine tailings, evaporation significantly dries the upper half of the profile and causes steady upward flux from the water table. Results will be useful in managing the disposal of tailings.