考虑力链结构拓扑演化的堆石体细观变形机理

The rockfill dam is one of the important dams in hydraulic engineering, and the prediction and control of the dam deformation are vital to the safety of high rockfill dams. At present, the mechanical characteristics of rockfill materials are not fully understood, as well as the deformation mechanism of the high rockfill dam. Traditional macroscopic methods meet difficulties in describing the complex mechanical characteristics of rockfill materials, therefore investigations on the mesoscopic structures of rockfill materials become important. The force chain is a significant mesostructure in granular materials, including the rockfill materials, and the evolution of its topological characteristics will correlate to the macroscopic deformation of granular materials. Characterizing and analyzing the topological structures rationally within force chains should be a proper way to explore the deformation mechanism of rockfill materials. This project will be progressed by adopting the theoretical methods, DEM simulations and laboratory tests. The contents include three aspects: topological characterization of the force chain in rockfill materials, investigation on the evolution mechanism of the force chain topological structures during the shear test and the relationship between the topological evolution and the macroscopic deformation. This project will finally present the mesoscopic mechanism of the rockfill deformation in a quantitative way based on the rational characterization of the force chain topological structure. The research achievement may promote the development of mesomechanics of rockfill materials, and provide inspirations for calculation and design of rockfill dam engineering.

堆石坝是水利枢纽工程中一种主要的挡水建筑物，坝体变形预测和控制对高堆石坝安全至关重要。目前我们对筑坝堆石体物理力学性质及高堆石坝的变形破坏机理认识不足。由于传统宏观方法难以反映堆石体的复杂变形性质，堆石体细观结构研究成为认识堆石体力学性能的重要手段。力链是堆石体等颗粒材料内部重要的细观结构，其拓扑特征的演化与堆石体的宏观变形有关。合理表征并定量分析堆石体内部的力链拓扑结构，是堆石体变形机理研究的有效途径。本项目将采用理论研究、离散元数值模拟、物理试验等手段，进行堆石体力链结构的拓扑属性表征、剪切过程中堆石体力链拓扑结构的演化规律、力链拓扑演化与宏观变形的内在联系三方面的研究。通过本项目的研究，可基于力链拓扑结构的合理表征，定量表达堆石体宏观变形的细观机制。研究成果有助于推动堆石体细观力学的发展，为堆石坝工程计算和设计提供参考。

堆石坝是水利枢纽工程中一种主要的挡水建筑物，筑坝材料堆石体的变形预测和控制对高堆石坝安全至关重要。力链是堆石体等颗粒材料内部重要的细观力学结构，其拓扑特征的演化与堆石体的宏观变形机制密切相关。本项目进行了堆石体颗粒体系力链结构的拓扑属性表征、剪切过程中颗粒体系力链拓扑结构的演化规律、力链拓扑演化与颗粒体系宏观变形的内在联系三方面的研究。本项目取得以下进展：1) 系统开展了不同条件下颗粒体系力链接触网络拓扑结构特征研究。采用不同阈值划分强接触系统并研究了强接触体系中的最大簇特征，根据复杂网络参量分析，发现各向异性应力状态下颗粒体系的强接触网络拓扑特征具有更多的一致性，且链状特征的接触结构多发生在1.5倍平均接触力划分的强接触体系中。2) 研究了颗粒形状对颗粒材料宏观响应和细观拓扑结构演化的影响。基于多组不同形状特性的堆石体常规三轴及真三轴加载试验，发现椭球颗粒体系等复杂形状颗粒体系内部力链拓扑参量指标与应力路径等无关，有助于进一步认识颗粒体系拓扑结构的统一性特征。3) 分析了颗粒体系剪胀（剪缩）的微细观起源。将接触网络剖分成多边形拓扑结构并根据拓扑演化定义新生、消失和不变三类细观结构，偏应力加载过程中新生力环结构能够表现出更加明显的剪胀特性和局部各向异性，颗粒体系整体的剪胀变形受到新生结构拓扑变化及恒定结构几何变化的综合影响。通过本项目的研究，有助于进一步认识堆石体等颗粒材料的复杂力学属性，为堆石坝工程设计施工提供一定的理论参照。