Energy dissipation in granular materials

自从库仑的工作平衡和破坏的粒状边坡，摩擦和强度的粒状土壤成为牢固地联系在一起。两个多世纪后，许多理论已经提出，导致库仑摩擦角和土壤颗粒之间的摩擦角之间接近一比一的比例。试图验证这些理论的实验产生了一个令人惊讶的迹象，宏观和微观摩擦角之间的联系远远弱于过去的理论暗示。尽管粒状土的抗剪强度特性与摩擦系统的抗剪强度特性相似，但颗粒间摩擦力与其缺乏直接联系的观点并不容易合理化。这指出了一个基本的知识缺口，可能解释了通过实际可用的模型描述土壤工程特性的许多困难。拟议的项目是要大大缩小这一差距，无论是在颗粒材料的行为中的摩擦作用的基本理解，并在开发一个本构模型的基础上充分的物理。这两个目标都连接到更广泛的主题的物理机制的能量耗散在粒状材料和它的分析描述建模的目的。该项目本质上是理论性的，但涉及粒子级模拟，以及利用传感技术最新进展的颗粒级物理实验。

Ever since Coulomb's work on equilibrium and the failure of granular slopes, friction and strength of granular soils became firmly linked. More than two centuries later, many theories have been advanced resulting in a near one-to-one proportionality between Coulomb's friction angle and the angle of friction between soil grains. Attempts to verify these theories experimentally yield a surprising indication that the link between macro and micro friction angles is far weaker than past theories implied. Although shear strength characteristics of granular soils appear analogous to those of a frictional system, the lack of a direct link to interparticle friction is not easily rationalizable. This points to a fundamental knowledge gap that possibly explains the many difficulties in describing engineering properties of soils through practically usable models. The proposed project is to substantially close this gap, both in terms of the fundamental understanding of the role of friction in the behavior of granular material and in developing a constitutive model based on adequate physics. Both objectives are connected to the broader topic of the physical mechanisms of energy dissipation in granular materials and its analytical description for modeling purposes. The project is theoretical in its nature but involves particle-level simulations, as well as grain-scale physical experimentation utilizing recent advances in sensing technology.