Document Type

Dissertation

Degree

Doctor of Philosophy (PhD)

Major/Program

Civil Engineering

First Advisor's Name

Seung Jae Lee

First Advisor's Committee Title

Committee Chair

Second Advisor's Name

Hector R. Fuentes

Second Advisor's Committee Title

Committee Member

Third Advisor's Name

Abdelhamid Meziani

Third Advisor's Committee Title

Committee Member

Fourth Advisor's Name

Atorod Azizinamini

Fourth Advisor's Committee Title

Committee Member

Keywords

morphology, volume, surface area, size, granular material, course aggregate, multiscale mechanics

Date of Defense

9-13-2019

Abstract

Granular materials such as soil and aggregate, are ubiquitous in nature and the understanding of their mechanical behavior is of great importance to better predict and design the civil infrastructure. The particle geometry is a key information to robustly establish the link between the underlying grain-scale mechanisms and the macroscopic behavior of granular materials. However, the characteristics of the particle geometry remain to be better understood. For example, we do not know how the volume is related to the surface area for irregularly shaped particles in general. Their relation clearly depends on the morphology, dictating that volume, surface area, and morphology are interrelated. Then, the remaining question is how the size of a particle would be related to those three geometric properties. The interrelation of these four geometry parameters is the key information to fundamentally understand their concerted influence on the complex behavior of granular materials, but we do not have the answer in the body of knowledge yet.

The research in this dissertation advances the understanding of grain-scale origin of the complex macroscale behavior of granular materials and creates a set of new knowledge as follows: (i) This study systematically addresses the influence of coarse aggregate angularity on cemented granular materials. It shows that cemented granular materials with round aggregates have superior small-strain performance, while the materials with angular aggregates have superior large-strain performance; (ii) This study develops a new theory for comprehensive 3D particle geometry characterization by proposing a formulation M = A/V×L/6, which translates the 3D particle morphology M as a function of surface area A, volume V, and size L; (iii) This dissertation is benefited by the early adoption of 3D-printing for geomechanical testing. Laboratory direct shear tests have been conducted on 3D-printed synthetic particles with different geometry, to robustly correlate the geometric properties of particles to geomechanical properties of the granular materials. (iv) This study unravels, for the first time, the power law relationship between A/V ratio and V for coarse aggregate in nature. This relationship is the key to predict morphology using volume measurement only, thus significantly reducing the effort of particle geometry characterization.

Identifier

FIDC008868

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