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Author ORCID Identifier


Open Access Dissertation

Document Type


Degree Name

Doctor of Philosophy (PhD)

Degree Program

Civil and Environmental Engineering

Year Degree Awarded


Month Degree Awarded


First Advisor

Ching S. Chang

Subject Categories

Geotechnical Engineering


Heterogeneous granular soils are ubiquitous in nature and man-made deposits. Heterogeneity of soil is characterized by its particle size distribution (or fines content for gap-graded soils). The particle size distribution of soil is the main factor that affects its mechanical properties. However, in soil mechanics, the influence of particle size distribution on mechanical properties is only considered in an empirical manner. There are few analytical methods that can explicitly account for the effect of particle size distribution. In this study, there are two purposes: 1) to develop a particle packing theory for modeling the effect of particle size distribution on density states of granular soils, including densest, loosest, and critical density states, which are the fundamental properties relating to mechanical behavior of soil, and 2) to study the shear behavior of granular soils with influence of particle size distribution. The developed particle packing theory is able to predict the density state of multi-sized soils based on their particle morphological characteristics and particle size distribution. The particle packing theory providing an ability to analyze the effect of particle size distribution is important in the understanding of mechanical behavior due to the heterogeneity of soil. Based on the developed particle packing theory, a framework of modeling the critical state line of granular soils was established by explicitly considering their particle size distribution. Incorporating the evolution of particle size distribution due to particle breakage into the model, this framework can be used for predicting the critical state line of granular material with particle breakage. A series of drained triaxial compression tests on dense binary silica sand mixtures with 4 different particle size ratios was performed to systematically investigate the effects of fines content and particle size ratio on the drained shear behaviors. It was observed that both fines content and particle size ratio have significant influence on the drained shear behaviors of binary granular soil mixtures. A mechanism was proposed to illustrate the influences of fines content and particle size ratio on the drained shear behavior from the perspective of particle column buckling. The findings from this research is potentially useful for analyzing geotechnical engineering problems, such as liquefaction of silty sand, landslides of weathered soil, levee failure due to erosion of fine particles, and dam instability due to grain crushing. This study also has potential to be applied in the continuum mechanics for materials of heterogeneous nature.


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Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.