双轴压缩条件下散粒体的二维孔隙分布及演化规律研究

发布时间：2018-05-28 08:07

本文选题：散粒体 + 孔隙结构　；参考：《岩土工程学报》2015年03期

【摘要】：基于离散单元法建立了不同密实度的理想散粒体数值模型,通过Voronoi Delaunay网格剖分建立离散域,采用基于边界点的椭圆拟合算法模拟散粒体中的孔隙,并进一步分析了在双轴压缩条件下散粒体孔隙的分布特征与演化规律,同时结合数值试样中单孔隙的变化过程,分析了散粒体变形的微细观力学机理。研究表明,散粒体二维孔隙表现出明显的双峰分布特征,在双轴压缩条件下,不同密实度散粒体的孔隙要素表现出明显不同的演化特征。总体说来,松散试样小孔隙比例增加,大孔隙比例减少,孔隙趋于均匀;而密实试样小孔隙比例减少,大孔隙比例增加。孔隙的排列方向与荷载主方向有关,初始密实度对其影响不大。双轴加载过程中长轴沿水平方向的细长孔隙首先崩溃,长轴沿轴向加载方向的孔隙存留下来并在散粒体变形过程中起主导作用,最终沿加载方向产生一个稳定的颗粒结构。单孔隙的发展过程显示,大孔隙上承担着较强的力链,双轴压缩过程中随着变形的发展,松散试样中接触力链较强的单个大孔隙逐渐分裂成为多个小孔隙,颗粒接触力链分布趋于均匀;而在密实试样中,随着变形发展小孔隙逐渐融合形成大孔隙。
[Abstract]:Based on the discrete element method, an ideal granular numerical model with different density is established. The discrete domain is established by Voronoi Delaunay mesh generation, and the pores in the granular body are simulated by elliptic fitting algorithm based on boundary points. Furthermore, the distribution and evolution of granular pores under biaxial compression are analyzed, and the micromechanical mechanism of particle deformation is analyzed in combination with the variation process of single pore in numerical samples. The results show that the two-dimensional pores of granular bodies exhibit obvious bimodal distribution and the pore elements with different densities exhibit distinct evolution characteristics under biaxial compression. In general, the small porosity ratio of the loose sample increases, the macropore ratio decreases, and the porosity tends to be uniform, while the small porosity ratio of the dense sample decreases and the macroporosity ratio increases. The orientation of pore arrangement is related to the main direction of load, but the initial compactness has little effect on it. In the biaxial loading process, the slender pores along the horizontal direction of the long axis first collapse, the pores along the axial direction of the long axis remain and play a leading role in the deformation process of the granular body, and finally a stable particle structure is produced along the loading direction. The development process of the single pore shows that there is a strong force chain in the macropore, and with the development of the deformation in the biaxial compression process, the single macropore with strong contact force chain in the loose sample gradually splits into several small pores. The distribution of the contact force chain of particles tends to be uniform, while in the dense sample, the small pores gradually fuse to form macropores with the development of deformation.
【作者单位】：北京科技大学土木与环境工程学院土木工程系;
【基金】：国家自然科学基金项目(51178044) 新世纪优秀人才资助项目(NCET-11-0579) 北京市高校青年英才资助项目(YETP0340)
【分类号】：TU411

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