A DEM Study of the Evolution of Fabric of Coarse-Grained Materials during Oedometric and Isotropic Compression
Granular materials like sandy and gravely soils are composed of an assembly of individual particles. A given soil deposit or specimen has a specific arrangement of individual particles, clumps of particles, and void spaces, which along with the orientation of inter-particle contacts, encompasses the basis of the soil fabric concept. Experimentally soil, fabric can be quantified by non-destructive methods such as image microscopy and X-ray computed tomography. While these state-of-the-art methods provide accurate and useful information, they require specialized equipment and analysis methods. This has ushered a rapid increase in the use of particle-based numerical tools, such as the discrete element method (DEM), which enable the study of behaviors at the micromechanical- and element-scales. In this paper, we investigate the behavior of specimens in oedometric (1D) and isotropic compression using 2D DEM simulations. To quantify the fabric of the specimens in DEM, scalar descriptors (void ratio, coordination number, and number of rattlers) and vector fabric descriptors (contact normal direction, contact normal forces, and shear forces) were monitored at different stages of oedometric and isotropic compression. The results presented herein provide a comparison of the trends captured by the different fabric descriptors and highlight the effect of fabric anisotropy on the macroscopic response.
Keywords: Fabrics, Particles, Compression, Grain (material), Isotropy, Numerical analysis, Discrete element method, Numerical methods