ISSN 2319-5347, ISI Impact Factor: 0.763

VOLUME 05 NO. 01 JANUARY 2016:

Title:        Modeling the Behavior of Granular Materials under Plane Strain Compression by 3D DEM
Authors:    Md. Mahmud Sazzad, Ripon Kumer Shaha, Md. Shehabul Islam
Abstract:   The in-situ stress condition in dam or embankment of roads corresponds well to the plane strain condition. In this study, simulation of plane strain compression (PSC) test was numerically performed to explore the behavior of granular materials such as sand at macro- and micro-scale using the discrete element method (DEM). Three cubical shaped samples having different void ratios were numerically prepared using eleven different sizes of spheres whose diameters range from 3 to 4 mm. The spheres were randomly placed in a cubical shaped sample in such a way that, at the initial stage, no sphere can touch the other and later, the sample was compressed isotropically to 100 kPa at different stages using the periodic boundary. The isotropically compressed samples were used for numerical experiment under PSC. It is noted that the numerical results are consistent to that observed in the experiments under PSC for different void ratios. Evolution of dilatancy index is observed and found to be dependent on the void ratio of the samples, in particular at the small strain level, for PSC. However, it is observed that the dilatancy index curves approach a unique state at large strain. The normalized work (normalized by the mean stress) exhibits almost unique behavior, particularly at small strain level, regardless of the void ratio. The evolution of the ratio of strong contacts to total number of stable contacts (a stable contact is a contact that have met a certain stability requirement, i.e., each particle has at least three contacts) with axial strain is also monitored and it is noted that the ratio is not a function of initial void ratios of the samples. The number of strong contacts, on an average, is the 30% of the total stable contacts in an assembly of granular system during shear regardless of the void ratios of samples.

Keywords: Plane strain compression, Dilatancy index, Micro parameters, Discrete element method.
Pages:         35-39

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