Evaluating preferential flow in an experimental waste rock pile using unsaturated flow and solute transport modeling

摘要

Numerical modeling of flow and conservative solute transport is useful to investigate the role of preferential flow and matrix flow in waste rock piles. In addition, the mechanisms determining the response of basal discharge to seasonal variations in precipitation can be investigated. This paper presents the results of simulations for an experimental waste rock pile at the Antamina mine, Peru. The pile (Pile 2) is composed of relatively fine-grained intrusive material. A uniform flow and transport formulation based on Richards equation was used for the simulations. Simulated basal discharge and cumulative outflow compare well to field observations. However, solute transport modeling was not able to reproduce the observed tracer breakthrough in the basal lysimeter. These results demonstrate the importance of preferential flow not only in rock-like, but also in soil-like waste rock piles and indicate that calibrating an unsaturated flow model to observed outflow alone is insufficient to evaluate flow patterns and residence times in mine waste rock.