Perpustakaan Digital ITB

The Discrete Element Method (DEM) has been increasingly used to study the behaviour of rock. Despite the advantage of classical DEM formulations in using simple interaction laws to model fracture initiation and propagation, they have limitations to properly simulate brittle rock behaviour. The code cannot predict the high values of unconfined compressive strength/tensile strength (UCS/TS) ratio associated with non-linear failure envelopes, as observed for hard rock, such as granite, unless significant modifications are made. This paper proposes and implements a clumped-particle model into a two-dimensional DEM code. The increase in the interaction between discrete elements, which locally increases the density of interparticle bonds, can improve the results to obtain the desired values of UCS/TS ratio. This approach seems able to significantly increase both the potential and the predictive capabilities of DEM for rock modelling purposes. The novelties introduced in this work are the presentation of a numerical procedure to determine the equivalent micro-mechanical properties of intact rocks and, aware of a gap in our knowledge, the characterisation of uncertainties that a clumped-particle model introduces in the numerical results. A series of numerical simulations, including uniaxial compression and direct tension tests, were carried out, by varying the relation between the clump and the minimum particle radius, using the Monte Carlo simulation technique. The results were compared with experimental data on Lac du Bonnet granite, from the bibliography, which allowed to determine the equivalent micro-mechanical properties. Results, from a simulation using a core sample of Lac du Bonnet granite, show that the variance in the values of the mechanical properties calculated decreases with the decrease in the particle radius, but the influence of the clump size on the behaviour requires the execution of a considerable amount of simulations to achieve results with an acceptable relative error of 5%. Nevertheless, the mechanical behaviour obtained from DEM simulations was in good agreement with the experimental data and the model captured both the tensile and the unconfined compression strength values.