Energy dissipation in granular materials

自从库仑关于平衡和颗粒斜坡破坏的工作以来，颗粒土的摩擦力和强度变得牢牢地联系在一起。两个多世纪后，许多理论被提出，导致库仑摩擦角和土壤颗粒之间的摩擦角几乎是一对一的比例。对这些理论进行实验验证的尝试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比过去的理论所暗示的要弱得多。尽管颗粒土的剪切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化的。这指出了一个基本的知识鸿沟，这可能解释了通过实际可用的模型来描述土壤的工程性质的许多困难。拟议的项目旨在大幅弥合这一差距，无论是在对摩擦在颗粒材料行为中的作用的基本理解方面，还是在开发基于适当物理的本构模型方面。这两个目标都与更广泛的主题有关，即颗粒材料中能量耗散的物理机制及其用于建模目的的分析描述。该项目本质上是理论上的，但涉及粒子级模拟，以及利用传感技术的最新进展进行的颗粒级物理实验。

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.