EAGER: Prototyping three-dimensional printing of sand columns for granular physics experiments

该项目旨在三维打印沙粒和沙柱，复制天然沉积砂的矿物模量、弹性模量和微观结构。研究者将收集未受干扰的自然沉积砂，制作热塑性砂、玻璃砂和粉末烧结砂，制作热塑性砂和烧结砂组成的砂柱，并比较制作砂粒和自然沉积砂柱的材料性能。该项目是探索性的，将需要多个参数测试和/或试验和错误来改进流程。高风险高回报的产品将是打印烧结颗粒，同时保留其微观结构。这些技术的成功开发将为砂的微观力学、景观演化和地质灾害预测开辟几条新的研究途径。这项工作还扩大了三名早期职业黑人在地球科学领域的参与。该项目将为攻读博士学位创造一个过渡阶段，包括参加加州大学圣地亚哥分校的“竞争优势”项目，这是一个为期六周的项目，旨在让少数族裔研究生有机会在开始研究生课程之前开始研究，并适应校园环境。该项目将评估沉积物收集、图像处理、三维打印和后期打印技术的结合是否能产生充分复制天然砂行为的沙粒和沙柱。如果成功，沙粒和沙柱的三维打印将为岩石物理学家、地球物理学家、沉积学家、地貌学家、工程师和颗粒物理学家开辟新的研究途径。作为一名岩石物理学家和地球物理学家，3d打印将允许研究者以新的方式询问一些问题，包括：(1)颗粒结构对易于引发滑坡、液化和地震的颗粒屈曲的影响是什么？(2)在压实、断裂带剪切、土壤和边坡蠕变、接触蠕变老化过程中发生的颗粒流的基本理论是什么？(3)对砂土抗变形能力有强烈影响的力链分布如何受颗粒特性的控制？这些问题涉及到几个尚未解决的地质灾害过程，我们无法很好地预测这些过程，部分原因是砂的物理性质可以结合起来产生大量的力学行为。这项提议的工作将激发科学界的新研究，使我们更接近于理解控制沙子力学行为的基本物理学，同时通过更好的灾害预测和自然资源识别来帮助拯救或改善生命。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project aims to three-dimensional print sand grains and columns that replicate the mineral moduli, elastic moduli, and microstructures of naturally-deposited sands. The investigator will collect undisturbed naturally-deposited sands, fabricate thermoplastic, glass, and powder sintered grains, fabricate sand columns composed of thermoplastic and sintered grains, and compare the material properties of fabricated and naturally-deposited sand grains and columns. This project is exploratory and will require multiple parameter testing and/or trials and errors to refine the processes. The most high-risk high-payoff product will be printing sintered grains while preserving their microstructures. The successful development of these techniques will open several new research avenues in the micromechanics of sands, landscape evolution, and geohazard predictions. This work also broadens the participation of three early-career black men in Geoscience. The project will create a transition to Ph.D. program that will include participating in the University of California San Diego’s Competitive Edge, which is a six-week-long program that aims to give minoritized graduate students an opportunity to begin research before the start of their graduate program and to acclimate to the campus environment.This project will assess whether a combination of sediment collection, image processing, three-dimensional printing, and post-print techniques can produce sand grains and columns that adequately replicate the behaviors of natural sands. If successful, three dimensional printing of sand grains and columns will open new avenues of research for rock physicists, geophysicists, sedimentologists, geomorphologists, engineers, and granular physicists. As a rock physicist and a geophysicist, some questions that 3-D printing will allow the investigator to interrogate in new ways include: (1) what is the influence of grain texture on buckling of grains, which tend to trigger landslides, liquefaction, and earthquakes? (2) what is the fundamental theory governing granular flow, which occurs during compaction, fault zone shearing, soil and hillslope creep, and contact creep aging? (3) how do grain properties control force chain distributions, which strongly influence the resistance of sands to deformation? These questions relate to several unanswered geohazard processes that we cannot predict well partly because sands’ physical properties can combine to create a vast range of mechanical behaviors. The proposed work will inspire new research in the scientific community and bring us closer to understanding the fundamental physics that controls sands’ mechanical behaviors while helping to save or improve lives via better hazard forecasts and natural resource identification.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.