Energy dissipation in granular materials

自从库仑对颗粒边坡的平衡和破坏的研究以来，摩擦和颗粒土的强度就紧密地联系在一起了。两个多世纪后，许多理论的发展导致库仑摩擦角与土壤颗粒之间的摩擦角之间几乎成正比。通过实验验证这些理论的尝试得出了一个令人惊讶的结论，即宏观和微观摩擦角之间的联系远比过去的理论所暗示的要弱。虽然颗粒土的抗剪强度特性看起来类似于摩擦系统，但缺乏与颗粒间摩擦的直接联系是不容易合理的。这指出了一个基本的知识差距，这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。拟议的项目是实质性地缩小这一差距，无论是在摩擦在颗粒材料行为中的作用的基本理解方面，还是在开发基于充分物理的本构模型方面。这两个目标都与颗粒材料中能量耗散的物理机制及其建模目的的分析描述这一更广泛的主题有关。该项目本质上是理论性的，但涉及粒子级模拟，以及利用最新传感技术的颗粒级物理实验。

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.