Examination of the Strength and Dilatancy of Granular Materials using 3D Printed Soil

砂和砾石的强度和刚度的测定是许多土木工程结构（如建筑物和桥梁基础、堤防、土坝和挡土墙）设计和施工的一个非常重要的组成部分。岩土工程师知道，强度和刚度是颗粒形状和质地，以及土壤密度和它所承受的压力的函数。然而，天然砂和砾石在矿物学、表面粗糙度、尺寸分布和颗粒形状上各不相同，因此很难清楚地了解这些变量如何影响土壤。S工程性质。这项研究试图将一种新技术——3D打印——应用于经典的土力学问题，以一种自然土壤无法实现的方式重新审视土壤强度。即使颗粒形状或尺寸分布发生变化，3D打印颗粒也能保持相同的材料和表面特性。该特性允许检测颗粒形状的直接影响。3D打印颗粒颗粒的实验室实验将用于完善当前的土壤行为理论。如果能够通过描述形状来更好地预测砂砾的行为，将极大地推动土力学、岩土工程、路面材料和材料处理工艺等领域的最新进展。此外，3D打印土壤的使用提供了一种协同的方法来教授本科生和研究生的基本土壤行为。临界状态土力学为分析土壤行为提供了一个有用的框架，但是对大型土壤数据库的需求以及对膨胀和强度之间独特关系的缺乏阻碍了它在实践者和本科土力学课程中得到更广泛的接受。由于临界状态剪切角主要取决于矿物学，因此抗剪峰值角取决于与剪胀相关的强度分量，因此取决于形状。本研究测试了一个假设，即3D打印颗粒可以作为模拟颗粒土，通过系统地改变形状，同时保持材料特性不变，来研究膨胀率和强度之间的关系。实验数据不仅有助于证明这种关系，而且还有助于验证可用于检查颗粒尺度响应的离散元方法（DEM）模型。了解剪胀环境下的基本行为将有助于加深对许多更复杂的岩土工程问题的理解，包括：液化、桩侧摩擦、承载力、边坡稳定性和现场测试（锥贯试验、标准贯入试验）。

The determination of the strength and stiffness of sands and gravels is a very important component of the design and construction of many civil engineering structures such as building and bridge foundations, levees, earth dams and retaining walls. Geotechnical engineers know that strength and stiffness are a function of grain shape and texture, as well as the density of the soil and the pressure it is subjected to. However, natural sands and gravels vary in mineralogy, surface roughness, size distribution, and particle shape making it very difficult to gain a clear understanding of how these variables affect the soil?s engineering properties. This research seeks to apply a novel technology, 3D printing, to a classical soil mechanics problem to reexamine soil strength in a way that is not possible with natural soils. 3D printed particles maintain the same material and surface properties even when the particle shape or size distribution is varied. This feature allows for the direct influence of particle shape to be examined. Laboratory experiments on 3D printed granular particles will be used to refine current theories of soil behavior. Being able to better predict the behavior of sands and gravels on a description of shape would greatly advance the state-of-art in the fields of soil mechanics, geotechnical engineering, pavement materials, and material handling processes. In addition, the use of 3D printed soil provides a synergistic approach to teaching fundamental soil behavior at the undergraduate and graduate levels. Critical state soil mechanics provides a useful framework for analyzing soil behavior, but the need for large soil databases and the lack of a unique relationship between dilatancy and strength hinders its more-wide acceptance among practitioners and undergraduate soil mechanics classes. Because the critical state shearing angle is mostly dependent on mineralogy, the peak angle of shearing resistance depends on a dilatancy-related component of strength, and thus it depends on shape. This research tests the hypothesis that 3D printed particles can be used as an analog granular soil to investigate the relationship between dilatancy and strength by systematically varying shape while keeping the material properties the same. Not only will the experimental data be useful to demonstrate this relationship, but it will also be instrumental in the validation of discrete element method (DEM) models which can be used to examine the particle-scale response. Understanding the fundamental behavior in a dilatancy context will contribute to an increased understanding of numerous, more complex geotechnical problems including: liquefaction, pile side friction, bearing capacity, slope stability, and in situ testing (Cone Penetrometer Test, Standard Penetration Test).