中文摘要：

在已有的变粒径建模方法基础上,针对不同粒径区宏观弹性不一致和界面区大小颗粒互相渗入两个问题进行优化。通过在近场核心区域采用小粒径颗粒模拟真实土颗粒,远场边界区域逐级放大颗粒粒径,不同粒径之间采用相同密实度的混合粒径模拟,实现三维大尺度离散元模拟,以减少模拟颗粒数量提升运算速度。基于宏观弹性一致条件,建立静力条件下几何上等比例放大颗粒体系的颗粒材料参数尺度关系,并满足应力、应变和应变能一致性,通过三轴模拟验证了宏观弹性一致性。在变粒径交界处设置密实度与均一颗粒区一致的混合层有效防止大小颗粒互相渗入,变形特性与均一颗粒区趋于一致,并提出了两种粒径颗粒混合生成特定密实度的方法。最后,通过模拟静力触探试验（CPT）,表明该方法的有效性。该方法可为三维离散元模拟工程大尺度问题提供新途径。

英文摘要：

A refinement method is proposed to solve the difference in the macroscopic elasticity and the interpenetration in interface area between different particle-size areas in the DEM. In simulations of 3D DEM large-scale problems, small balls are used in the near field core area to simulate the real soil, while the far field boundary regions are filled with larger balls. In addition, a mixed area is set between different particle-size areas with the same relative density. The number of particles in the model can be reduced enormously, which improves largely the calculation efficiency. For scaling particle systems, the scale relationship is established on the static condition by the identical macro elasticity of uniform granules. The relationship satisfies the consistency of stress, strain and strain energy. The results of a series of triaxial test simulations verify the uniformity of macro elasticity. A method to generate a certain density mixture with two different particle sizes is proposed. The results of DEM simulations illustrate that the deformation property of mixed area is consistent with that of the uniform particles. Finally, the results of cone penetration test simulations show that the proposed method is effective. This study may provide a new approach to the application of 3D discrete element modelling in the large-scale geoteehnical engineering.