Analytical Modeling for the Effect of Grain Size Distribution on the Critical State of Granular Soil

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Natural soil is composed of particles of various sizes. Observed from experiments, particle size distribution has long been recognized as an important factor that influences the strength of soil, and consequently influences the performance and stability of infrastructures founded on soil. Therefore, it is important to understand how the soil strength is influenced by the particle size distribution. However, currently there is no analytical model that can explicitly account for the effect of particle size distribution on soil strength. This award supports fundamental research to develop the essential knowledge for modeling the strength of soil with consideration of particle size distribution using the concept of critical state void ratio. The method developed from this research will be useful for geotechnical and earthquake engineering problems, such as landslides in weathered soil, levee failure due to erosion of fine particles, dam instability due to grain crushing, and liquefaction of silty sand. Results of this research can be used to reduce future risks of failures due to natural disasters, and to develop design methodologies which are safer and more resilient. Thus, results from this research have potential benefits to the U.S. economy and society. The results and activities of this research are integrated into courses on soil mechanics contributing to engineering education and researchThis research will address the fundamental issue on the role of particle size distribution in soil strength. The main goal of this research is to develop a particle packing theory for soils at critical state, considering the mix mechanism of particles of various sizes. Through the use of this theory, an analytical model will be developed that can predict the critical state void ratio of soil based on its particle size distribution. To facilitate the theoretical development, a series of experimental tests will be performed on soils with various types of grain size distribution. The intellectual merit of this research is twofold: (1) This investigation allows us to predict the soil strength from a fundamental perspective by using a novel approach of particle packing theory, (2) This investigation pushes forward the knowledge-boundary of continuum mechanics by providing a methodology for analyzing the behavior of particle assembly.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.