Influence of Particle Size Distribution on Density State of Soil

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Soil generally consists of particles of different sizes, and particle size distribution is the main factor that affects the mechanical properties of soil. However, in soil mechanics, the influence of particle size distribution on mechanical properties is only considered in an emperical manner. There is no analytical method that can explicitly account for the effect of particle size distribution. Thus, the ability to analyze the effect of particle size distribution is an important step in the understanding of mechanical behavior due to the heterogeneity of soil. This award supports fundamental research to develop the necessary knowledge for modeling the effect of particle size distribution. Results from this research will be useful for analyzing geotechnical engineering problems, such as liquefaction of silty sand, land slides of weathered soil, levee failure due to erosion of fine particles, and dam instability due to grain crushing. The method developed in this research can help reducing the future risks of failures, developing more robust design methodologies, and better targeted mitigation works. Therefore, results from this research has potential benefits to the U.S. economy and society. The resuts and activities of this research are incorporated into courses on soil mechanics contributing to the integration of engineering education and research. The main goal of this research is to develop a theory of a supplementary descriptor for the packing structure of soil based on its particle size distribution. Using this supplementary descriptor, a method is developed for predicting the density state of soil with arbitrary particle size distributions. To aid in the theoretical development, a series of numerical simulation tests using discrete element method and a series of laboratory tests are performed on soils with various types of particle size distribution. The intellectual merit of this research is twofold: (1) This investigation is based on a novel approach, which can mathematically categorize the packing structures of a soil based on its particle size distribution. This offers a rational way to predict the density state and other mechanical properties, (2) This investigation provides a useful methodology to analyze the behavior of heterogeneous material, which pushes forward the knowledge boundary of continuum mechanics.