基于离散元的颗粒材料中应变局部化形成与演化研究  

Research on the Initiation and Evolution of Strain Localization inGranular Materials Based on Discrete Element Method

作　　者：李易奥 周伟[1,2] 邹宇雄[1,2] 王頔 马刚 LI Yi-ao;ZHOU Wei;ZOU Yu-xiong;WANG Di;MA Gang(State Key Laboratory of Water Resources Engineering and Management,Wuhan University,Wuhan 430072,Hubei Province,China;Key Laboratory of Rock Mechanics in Hydraulic Structural Engineering of the Ministry of Education,Wuhan University,Wuhan 430072,Hubei Province,China;State Key Laboratory of Geomechanics and Geotechnical Engineering,Institute of Rock and Soil Mechanics,Chinese Academy of Science,Wuhan 430071,Hubei Province,China)

机构地区：[1]武汉大学水资源工程与调度全国重点实验室,湖北武汉430072 [2]武汉大学水工岩石力学教育部重点实验室,湖北武汉430072 [3]中国科学院武汉岩土力学研究所岩土力学与工程国家重点实验室,湖北武汉430071

出　　处：《中国农村水利水电》2024年第7期196-202,209,共8页China Rural Water and Hydropower

基　　金：国家重点研发计划项目课题(2022YFC3005503);国家自然科学基金项目(52322907、52179141)。

摘　　要：岩土颗粒材料的应变局部化失效问题广泛存在于工程设计应用中,主要表现为介观尺度上的应变局部化现象和宏观尺度上的剪切带产生,目前在微观尺度上的形成机理尚不明确。为了系统研究颗粒集合体的应变局部化的形成与演化过程,通过使用离散单元法(Discrete Element Method,DEM)模拟了指定平面应变加载路径的真三轴试验,获取了宏观和微观尺度上的颗粒材料几何、运动以及力学信息。为了找出表征应变局部化特性的最佳特征量,比较了颗粒温度、波动位移和局部剪胀角等微观指标,发现波动位移在表征应变局部化方面与其他参数相比相关性更好,并选定其作为应变局部化表征变量。为了量化颗粒集合体从应变局部化开始产生到发育完成的具体应变区间,采用莫兰指数对波动位移的空间分布特征进行统计和分析,确定了颗粒集合体在弹塑性转换阶段的发育区间。进一步对颗粒集合体应变局部化发育区间内的波动位移空间分布进行探究,并统计不同空间区域内波动位移的概率密度函数,发现研究区域外部的局部塑性在过渡阶段停止演化,而内部塑性以逾渗模式发展。最终,通过波动位移的空间分布进行聚类分析,获得了描述介观尺度上应变局部化的团簇体模型。该模型可以将颗粒集合体宏观剪切带的形成与发育和单个颗粒的微观塑性发展相联系,刻画颗粒集合体从介观尺度上的应变局部化出现到宏观尺度上剪切带完全形成的演化过程。The strain localization failure problem of geotechnical granular materials widely exists in engineering design applications.Its main manifestations are strain localization at the mesoscale and shear band generation at the macroscale, and their microscopic mechanism is stillcurrently unclear. In order to systematically study the formation and evolution of strain localization in particle aggregates, a true triaxial testwith designated plane strain loading path is simulated using discrete element method (DEM), which provides thorough insights into the mate⁃rial geometry, motion, and mechanical information of granular materials on both micro- and macroscopic scales. To identify the optimal fea⁃ture quantity for characterizing strain localization characteristics, micro indicators such as particle temperature, fluctuation displacement,and local dilatancy angle are compared with each other. It is found that the fluctuation displacement has better correlation with other parame⁃ters in characterizing strain localization, so it is selected as the strain localization characterization variable. In order to quantify the specificaxial strain level from the onset of strain localization in particle aggregates to the completion of development, the Moran’s I is introduced tostatistically analyze the spatial distribution characteristics of displacement fluctuation, and the shear band development interval of particleaggregates during the elastic-plastic transition stage is determined. Furthermore, before the strain localization of particle aggregates fully de⁃veloped, the spatial distribution and the probability density function (PDF) evolution of displacement fluctuation indicates that the plasticityout of research region ceases to evolve in the transition stage, while the plasticity in research region increases in the mode of percolation. Fi⁃nally, a cluster model describing strain localization on mesoscopic scale is obtained through clustering analysis based on the spatial distribu⁃tion of displacement fluctuation.

关 键 词：颗粒材料 真三轴试验 非仿射变形 应变局部化 离散单元法 

分 类 号：TU43[建筑科学—岩土工程] TV641[建筑科学—土工工程]