3D Assessment of Particle Morphology and its Influence on Friction, Dilatancy, and Fabric Evolution of Sheared Granular Materials

非胶结颗粒材料的强度特性和变形特性在很大程度上源于颗粒结构的组构或几何形状以及颗粒间的摩擦。颗粒形态(表面粗糙度、圆度和球度)和微观特性对颗粒材料的工程行为有重要影响。颗粒材料在2D中的形态、组构和颗粒相互作用的定量描述是众所周知的，自20世纪70年代初以来一直是一个广泛的研究主题；然而，3D中的类似测量仍然非常有限。文献中缺乏一项系统的3D研究，通过实验研究颗粒的球度、形状和表面粗糙度对剪切颗粒材料的摩擦、剪胀和组构演化的影响。在这项研究中，将从高分辨率3D同步计算机断层扫描(SCT)图像和天然硅砂颗粒的表面粗糙度获得准确的定量测量颗粒形状和球度，并辅之以三轴样品中颗粒相互作用的原位3D SCT成像。这些测量将用于评估颗粒形态对颗粒材料的织物、摩擦、膨胀特性、临界状态和应变局部化的影响。这项研究将提供关键的实验测量来校准和验证模型，从而更好地理解颗粒材料的行为。此外，它还将回答有关影响颗粒材料强度特性的内在颗粒特性的关键基本问题。这一认识的增加将促进有关预测颗粒材料工程行为的新理论的发展。这项研究除了丰富土木工程和环境工程专业外，(I)将提供急需的实验测量方法，以校准处理沙的行为的模型；(Ii)将影响研究界并促进技术转让；(Iii)将使少数族裔/女性本科生参与尖端工程研究；(Iv)将为土木工程本科生提供丰富的研究经验；(V)将通过让高中生参与我们的研究，帮助吸引下一代科学家，激发他们对土木工程领域的兴趣，并有助于提高下一代土木工程教育工作者和专业人员的质量；和(Vi)将制作为初中生和高中生量身定做的新的尖端教育材料。

Strength properties and deformation characteristics of uncemented granular materials are to a large extent derived from the fabric or geometry of the grain structure and inter-particle friction. Particle morphology (surface roughness, roundness, and sphericity) and micro-properties play a significant role in influencing the engineering behavior of granular materials. Quantitative description of morphology, fabric, and particle interaction of granular materials in 2D is well understood and has been a subject of extensive research since the early 1970s; however, similar measurements in 3D are still very limited. The literature lacks a systematic 3D study that experimentally investigates the effects of particles sphericity, shape, and surface roughness on friction, dilatancy, and fabric evolution of sheared granular materials. In this research, accurate quantitative measurements of particle shape and sphericity will be obtained from high-resolution 3D synchrotron computed tomography (SCT) images and surface roughness of natural silica sand particles complemented by in situ 3D SCT imaging of particle interaction within triaxial specimens. These measurements will be used to assess the influence of particle morphology on fabric, friction, dilatancy properties, critical state, and strain localization of granular materials. This research will provide critical experimental measurements to calibrate and validate models allowing a better understanding of the behavior of granular materials. Also, it will answer key fundamental questions about intrinsic particle properties that affect strength properties of granular materials. This increased understanding will spur the development of new theories dealing with predicting the engineering behavior of granular materials. The research, besides enriching the Civil and Environmental Engineering program, (i) will provide much needed experimental measurements to calibrate models that deal with the behavior of sand; (ii) will impact the research community and promote technology transfer; (iii) will involve minority/female undergraduate students in conducting cutting edge engineering research; (iv) will provide an enriching research experience for undergraduate civil engineering students; (v) will help engage the next generation of scientists by involving high school students in our research, to spark their interest in the field of civil engineering and help contribute to the quality of the next generation of civil engineering educators and professionals; and (vi) will produce new, cutting-edge educational materials tailored for middle and high school students.