Development of a Waste Rock Simulation Model Including Placement Techniques to Minimize Environmental Impacts of Acid Rock Drainage

Abstract

This research aims to develop a model using a systems dynamics approach that can be coupled with TMSim to account for the deposition of waste rock at hard rock mines at the feasibility stage of mine planning. The model includes waste rock placement techniques to minimize the environmental impacts of acid rock drainage at many hard rock mines. The GoldSim software was used to develop the model, with two aspects, the deposition of waste rock based on mine processes to create the “pile”, and the environmental conditions and associated variably saturated flow of water within the waste rock pile.The conceptualization of the waste rock in the pile was constructed in four lifts. These four lifts were divided into 15 rows and 16 columns to create a pseudo 3-D structure of 240 1-D columns. The model includes waste rock deposition, precipitation, snowmelt, evaporation, runoff, infiltration, and seepage. The variably saturated system was modelled using a modified version of the variably saturated flow sub-model for a tailings cover. Modifications of the model included potential evaporation calculation, snow accumulation and meltwater calculation, and simplification of runoff. The model was run using a case study for a mine site at the feasibility stage to demonstrate the application of the model. Overall, the model behaved as expected with general pile water balance behaviour observed over the course of construction and long-term behaviour. The models clearly show the benefits of paddock dumping versus end dumping with reduced water storage volumes within the pile.