二维颗粒体系的力链网络结构及其宏观动力学响应研究

The granular matter is a system composed of a large number of discrete macroscopic particles, which are widely existed in the world. In granular matter, the external loading transfers selectively along the path (force chain) which formed by the contacted particles. Then the structure, the particle → the network of force chain → the system, is formed. Where the network of force chain is the skeleton of the granular matter, and it is an important factor determining the mechanical characteristics of the granular matter. Up to now, the quantitative study on force chain and its dynamical evolution is scarce. The three aspects which will be studied in this project are as following: (1) The photoelastic experiment and the discrete element simulation will be used to obtain the information of the force networks of the two-dimensional granular system. The spatial correlation function of the stress change of particle after perturbation will be built to quantify the structural characteristics of the force chain and the force networks. And the applicable scope of the continuous elastic medium model will be analyzed. (2) The dynamical response function will be built to analyze quantificationally the response of the system to the external perturbations. The evolution of the dynamical response of the granular system under various loadings will be studied; (3) The correlation of the soft spots, the rearrangement of granular and the stress change under various loadings will be built to explore the structural origin of the evolution of the networks of force chain. Obviously, the study of this project will build the correlation of the evolution of mesostructure and the macroscopic dynamics of granular. It will also expand the understanding on the nature of granular dynamics, and has important application value on guiding the engineering practice.

颗粒物质是由大量离散固体颗粒组成的体系，广泛存在于自然界中。在颗粒物质中，外载荷有选择的沿着颗粒相互接触形成的路径（力链）传递，形成颗粒→力链网络→体系的多尺度结构。其中，力链网络是骨架，是确定颗粒物质力学性质的重要因素。目前，关于颗粒物质力链及其动力学演化方面的定量研究比较薄弱。本项目拟开展以下3方面研究：（1）利用光弹实验和离散元模拟获取二维颗粒系统力网络的信息，构建扰动前后应力改变量的空间关联函数，量化力链及力网络的结构特征，分析连续弹性介质模型的适用范围；（2）构建体系的动力学响应函数，定量分析体系对各种外部扰动的响应，研究不同加载条件下颗粒系统动力学响应的演化规律；（3）建立不同载荷下体系中软点与颗粒重排及应力变化量的关联，探索力链网络演化的结构起源。显然，本项目的研究将建立细观结构演化与宏观动力学的关联，拓展人们对颗粒物质动力学的理解，并在指导工程实践方面具有重要的应用价值。

颗粒物质是由大量离散固体颗粒组成的体系，广泛存在于自然界中。在颗粒物质中，外载荷有选择的沿着颗粒相互接触形成的路径（力链）传递，形成颗粒→力链网络→体系的多尺度结构。其中，颗粒体系的介观结构（例如力链和软区）是确定颗粒物质力学性质的重要因素。目前，关于颗粒物质介观结构及其动力学演化方面的定量研究非常薄弱，本项重点目针对上述问题开展了以下3方面研究：（1）研究了颗粒体系力网络、接触网络及其力学性质随外部载荷的演化，对颗粒系统有序-无序转变、剪切不稳定性等问题展开系统研究，发表相关论文5篇；（2）搭建了用于测量颗粒体系有效质量谱和体积响应谱的实验装置，研究了垂直脉冲激励下外部载荷对有效质量谱及颗粒密度对颗粒体系体积响应谱的影响，发表了相关论文4篇；（3）搭建了一套用于测量颗粒体系声学参数的声学测试平台。利用该平台，本项目组测量了玻璃珠组成的颗粒介质样品的横波和纵波声速，同时分析了剪切模量(G)与体积模量(B)的比值(G/B)随压强的变化规律，实验验证了低压强下L玻璃态的存在，发表相关论文1篇。显然，本项目的研究将有助于建立介观结构演化与宏观动力学的关联，拓展人们对颗粒物质动力学的理解，并在指导工程实践方面具有重要的应用价值。