Granular Mechanics Across Length Scales: Contact, Breakage, Fracture, and Permeability

Abstract

Particle morphology is of pivotal importance in granular materials at different length scales. This thesis begins with quantification and reconstruction of real particle shapes, then studies various kinds of granular material behaviour influenced by morphology features. The project background and related previous work are introduced in Chapters 1 and 2, respectively. Chapter 3 is firstly concentrated on reconstructing particle shapes using Spherical Harmonics (SH). DEM clumps are also used to approximate realistic particle shapes to simulate sand column collapse. The efficiency of SH analysis between different coordinate systems in FEM mesh qualities and reconstruction are also compared. Chapter 4 is on contact behaviour of rough spheres with different morphology features. Via FEM simulation, benchmarked with Hertzian solution, a semi-analytical model is proposed. In Chapter 5, to highlight the influences of contact curvature on single particle crushing behaviour, a rotational point loading in FDEM, benchmarked with an in-situ XCT experiment, is proposed. In Chapter 6, experiments of failure modes of cemented sands under different loading paths and the quantification of fracture fabric are conducted. FDEM simulations, benchmarked with a combined in-situ experiment with XCT and diffraction, of meso-scale concrete are also conducted. Effects of realistic aggregate morphology on overall concrete are investigated. In Chapter 7, permeability of uniformly graded 3D printed grains, is experimentally studied. Modified Kozney-Carman equation is also proposed. Chapter 8 concludes this work by summarising the findings and implications and provides an outlook on future works. This dissertation presents a new comprehensive understanding of granular behaviour influenced by its morphology features. Via the proposed framework combining both experimental and numerical information, it is helpful to design and optimise of various granular materials with specific morphology features.