Influence of Particle Size Distribution on Density State of Soil

土体一般由不同大小的颗粒组成，而颗粒分布是影响土体力学性质的主要因素。然而，在土力学中，颗粒分布对力学性质的影响仅是经验性的。目前还没有一种分析方法可以明确地解释颗粒大小分布的影响。因此，能够分析颗粒分布的影响是理解由于土壤的非均质性而产生的力学行为的重要一步。该奖项支持基础研究，以开发对颗粒尺寸分布的影响进行建模的必要知识。研究成果对粉砂液化、风化土体滑坡、细粒冲刷破坏堤防、颗粒破碎失稳等岩土工程问题的分析具有一定的参考价值。这项研究中开发的方法可以帮助降低未来失败的风险，开发更健壮的设计方法，以及更有针对性的缓解工作。因此，这项研究的结果对美国经济和社会具有潜在的好处。这项研究的结果和活动被纳入土力学课程，有助于工程教育和研究的一体化。本研究的主要目的是发展一种基于土壤颗粒分布的土壤堆积结构补充描述符的理论。利用这一补充描述符，提出了一种预测任意粒径分布土壤密度状态的方法。为了辅助理论的发展，本文采用离散单元法进行了一系列的数值模拟试验，并在室内进行了一系列的室内试验。这项研究的学术价值有两个方面：(1)这项研究是基于一种新的方法，它可以根据土壤的颗粒分布对土壤的堆积结构进行数学分类。这为预测材料的密度状态和其他力学性能提供了一种合理的方法。(2)本研究为分析非均质材料的行为提供了一种有用的方法，推动了连续介质力学的知识边界。

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.