DEM modeling of mining operations

Nowadays, the storage of material coming from the mining process is performed in stockpiles of great size, which might face failure if the retrieving is not done correctly and if the repose angle is exceeded. This study aims to analyze a stockpile failure that occurred in northwest Italy by the distinct element method (DEM), specifically investigate if this numerical method can reproduce the process of creating stockpile and its possible failure. In this context, the distinct element method is a numerical method developed by (Cundall & Strack, 1979)based on Newton's second law of motion and the basic law of particle interaction, allowing to model material as a realistic mechanical system consisting of particles bonded by interaction forces or contact models. To test the hypothesis of whether the Distinct Element method can simulate the behavior of the stockpile, the commercial software PFC2D produced by Itasca is used. To model the conformation of the stockpile a hopper device was created, and cycles of load and discharge were performed. Regarding the excavation process, two methods were proposed. The first one aims to simulate the movement of a wheel loader bucket with two orthogonal walls that rotate at a fixed point. The second method consists of performing a vertical excavation by deleting the particles located at the toe of the stockpile. The material conforming the stockpile was calibrated using the method proposed by (Camusso & Barla, 2009) by confronting the macro-parameters obtained with the numerical analysis, with results of previous laboratory tests. The results showed that even though the stockpile's real size was not achieved, the proposed method to create it did simulate the real conditions properly. Regarding the retrieving process, both proposals showed a failure mode similar to the one observed in the case study, leading to a reduction of height, an increase of the width, and consequently reducing the slope angle. In conclusion, the Distinct Element method can successfully represent the material conforming a stockpile and its possible failure.