散粒介质临界状态细观力学结构特征的数值模拟与分析  

Numerical simulation and analysis of meso-mechanical structure characteristic at critical state for granular media

作　　者：刘洋 李爽 LIU Yang;LI Shuang(Department of Civil Engineering, School of Civil and Resources Engineering, University of Science and Technology Beijing, Beijing 100083, China)

机构地区：[1]北京科技大学土木与资源工程学院土木工程系,北京100083

出　　处：《岩土力学》2018年第6期2237-2248,共12页Rock and Soil Mechanics

基　　金：国家自然科学基金(No.51178044);北京市优秀人才培养资助项目(No.2013D009006000005)~~

摘　　要：基于离散单元法对不同密实度理想散粒体进行了双轴剪切试验的宏微观数值模拟,通过网格剖分将Voronoi多边形表征的loop单元作为散粒介质细观力学结构的基本单元,模拟了剪切过程中不同类型loop单元数量、几何形态和力学特征的演化过程,并重点分析了临界状态时散粒介质的细观力学结构特征。模拟结果显示,初始密实度不同的试样在向临界状态发展的过程中,高阶单元与低阶单元的发展规律完全不同,不同初始密实度试样中同阶loop单元的发展规律也不相同,但同阶loop单元的数量比例、几何形态、颗粒接触力及单元内滑动率最终均达到了各自的临界状态。从细观角度分析,散体介质的临界状态是高阶和低阶loop单元在荷载作用下相互转化的结果,是所有loop单元物理力学状态的综合平均与外在表现,临界状态时不同阶数的loop单元处于一个动态平衡状态,宏观上表现为常剪应力和常体积下剪切变形的不断发展。数值模拟结果也表明,loop细观结构单元包含了丰富的信息,其数量、几何形态、受力特征及接触稳定性的发展与散粒体的强度、剪胀以及临界状态的发展密切相关,可以将其作为散粒介质细观尺度的分析单元。The macro-and micro-numerical simulations of biaxial shear tests for ideal granular samples with different initial densities were carried out using discrete element method. Loop structures, represented by Voronoi polygons, were taken as the basic meso-mechanical unit of granular material by mesh-subdivision. The evolution of numbers, geometrical morphology and mechanical characteristic for different loops were simulated. The meso-mechanical characteristic at critical state for granular media was especially analyzed. Numerical results show that the evolution of higher-order loops and lower-order loops are different. The evolution of same types of loops in granular samples with different initial densities are different before critical state reaching. The number proportions, geometrical morphology, contact forces of side particles and inner sliding rates of same kinds of loops in granular samples with different initial densities have reached critical state respectively. From mesoscopic point of view, critical state of granular media is the consequence of mutual transformation for higher-order loops and lower-order loops, and is the combined average and external manifestation of all loops. Meso-scale loop structures under a state of dynamic equilibrium at critical state reflected by the constant shear stress and development of shear deformation under constant volume on macro-scale. Numerical results also show the evolution of numbers, geometrical morphology, mechanical characteristic and contact stabilities of meso-scale loop structures, are closely related to the development of strength, dilatancy and critical state for granular material. So it can be taken as the basic unit of meso-mechanism for granular media.

关 键 词：散粒介质 细观结构 临界状态 离散元法 

分 类 号：TU43[建筑科学—岩土工程]