Discrete element model simulations of failure processes of cohesive granular material

Yamaguchi, Y., 2022. Discrete element model simulations of failure processes of cohesive granular material. PhD, Nottingham Trent University.

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Granular materials, such as powder and sand, are all around us and are studied in engineering, industry and many other fields. For example, the rheological behaviour of rocks and soils are important in geology. Similarly, predicting internal deformation and failure of building materials consisted of granular particles is important in civil engineering. This thesis focuses on how emergent phenomena, such as shear failure, compaction failure or cluster formation in granular materials can be captured in a minimal model. In particular, I explore the effects of cohesion when an external force is applied to a granular aggregate, using discrete element model (DEM) simulations. I deal with two types of cohesiveness. The first project investigates cemented cohesive aggregates, which include solid, brittle bonds between grains, simulating porous rocks. While constraining all the simulation parameters by related experiments, I succeed in reproducing and extending the experimental observations on this material’s mechanical response to uniaxial compression. Then, I explore its failure processes, applied to brittle, ductile and low-density materials. I also show how machine learning can predict the failure timing of the material. The second project addresses the rheology of cohesive granulates. I investigate the effects of density and cohesion strength for a granular system under a constant pressure condition and shear deformation, by a combination of 2D and 3D simulations. Both simulations show cluster formation and shear localisation due to cohesion, and suggest that these phenomena are intrinsic to cohesive granular materials. I also measure a decrease in shear stress accompanying cluster formation. Finally, I also identified the existence of a critical nuclei size for cluster formation. Generally, this work together shows the strengths of a minimal, experimentally-informed model that can reproduce the emergent phenomena of cohesive granular materials and identify the key physical quantities that control these phenomena.

Item Type: Thesis
Creators: Yamaguchi, Y.
Date: October 2022
Rights: The copyright in this work is held by the author. You may copy up to 5% of this work for private study, or personal, non-commercial research. Any re-use of the information contained within this document should be fully referenced, quoting the author, title, university, degree level and pagination. Queries or requests for any other use, or if a more substantial copy is required, should be directed to the author.
Divisions: Schools > School of Science and Technology
Record created by: Linda Sullivan
Date Added: 24 Jan 2023 11:40
Last Modified: 24 Jan 2023 11:40
URI: https://irep.ntu.ac.uk/id/eprint/48056

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