Geotechnical Characterisation of Coarse Mine Waste Using DEM

SRK News | Issue 54: Rock Engineering and Slope Stability

A4   |   Letter

The study of the mechanical behaviour of mine wastes containing particles of metric order is a challenging task because commercial testing devices typically only accommodate samples composed of particles that measure a few centimeters. To overcome the equipment size limitations, testing of coarse material is conducted on samples prepared by modifying the particle size distribution (PSD) of the prototype material. Parallel scaling or material scalping are some of the techniques used to prepare coarse samples for laboratory testing. The testing sample may differ from the prototype both in the size of the particles and in the form of the PSD. Therefore, the mechanical behaviour of tested samples doesn’t represent the mechanical behaviour of the prototype material.

It is not trivial to define the corrections required to deduct the behaviour of a prototype material based on lab results obtained using samples that differ from it. This is due to the variety of factors that influence mechanical behaviour, which cannot be dissociated in physical investigations.

Discrete Element Method (DEM) can be used to compare the macro and micromechanical behaviour of model and prototype samples, alternating with decoupling some of the aspects that influence the behaviour, allowing them to define the corrections required for the laboratory results.

The open source code LMGC90 developed at the University of Montpellier, is dedicated to modelling large collections of interacting objects with complex mechanical behaviour. It is particularly suited for the study of frictional granular samples. Its algorithm is based on the Contact Dynamic (CD) Methods developed by Jean-Jacques Moreau and does not require elaborate calibration to predefine particle contact stiffness as other DEM methods require (e.g. Molecular Dynamics). Additionally, the heterogeneity of the particles in size and shape (polydispersity) can be considered.

Researchers in granular media, Emilien Azema from the University of Montpellier in France and Nicolas Estrada from the University of Los Andes in Colombia, are currently collaborating with the authors to implement LMGC90 in an investigation. This investigation seeks to develop a method to build models for mine waste prototypes that can be tested in the laboratory, where the mechanical behaviour of the prototype can be predicted, considering the effects that particle shape, particle size, particle size distribution and particle breakage resistance may have on the mechanical behaviour of coarse grained materials.

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