EAPSI: Modeling of Forces Within Sand During Compression Based on X-Ray Images

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The engineering behavior of granular materials has significant importance to geotechnical engineering, defense, and industry, and has been the subject of extensive research. Examples of granular material are: sand particles under a foundation, the flow of sand particles exposed to a buried explosion, pharmaceutical powders during processing, or grains within a silo. The interaction and forces between these particles is extremely important to the mechanical behavior of granular material but is still not very well understood. Dr. Antoinette Tordesillas, from the University of Melbourne in Australia, is a leading expert in the micro-mechanics of granular material and has developed a robust suite of mathematical tools to analyze granular materials data and measurements. This research will incorporate three-dimensional x-ray images of granular material during loading, provided by the proposer, to test and analyze in Dr. Tordesillas's models.As external loads are applied to mass of granular material, meso-scale columnar structures of particles known as force chains align in a nearly quasi-linear manner to resist the bulk of the applied load, and during the increase of loading the force chains will either continue to resist the load or buckle. Understanding how force chains behave given certain boundary conditions will help explain the macro-scale properties of the material and contribute to a micro-mechanical approach to modeling multi-scale behavior. Complex particle morphology and granular fabric, obtained from 3D X-ray computed tomography (CT) data of natural sand during, will be analyzed in the model and compared to the idealized particles. The research is expected to provide an insight into the factors that affect the formation and collapse of force chains which has a profound impact on computer models and practical applications that involve granular materials. This NSF EAPSI award is funded in collaboration with the Australian Academy of Science.