不同尺度分布散粒材料砂堆形成过程的二维离散元模拟

2D DEM simulation on the sandpile formation for granular materials with different grain size distributions

用作者开发的离散元程序,模拟不同尺寸分布的砂堆形成过程。把散体颗粒简化为圆形颗粒,模拟过程分三步:首先利用参考网格生成颗粒的松散堆积结构;为了避免颗粒下落的冲击作用对砂堆安息角的影响,先模拟颗粒在重力作用下在圆柱容器内的自由下落与堆积,直至堆积达到稳定;最后,移除容器,只保留一个底部边界,模拟颗粒体系的散落过程,直至形成一个稳定的砂堆。模拟结果表明,在其他参数保持相同的情况下,随着颗粒尺寸的减小,砂堆的安息角逐步减小并趋向于一常值。对模拟中的两组颗粒体系进行相同条件下的砂堆形成实验,结果表明,模拟与实验所得安息角大体相当。

The dynamic sandpile formation of granular materials with different size distributions have been numerically investigated using the Discrete Element Method （DEM） developed by author. The shape of grain has been simplified as disc particle. The simulating process can be divided into three steps. First, a loose packing of particles is generated by reference lattice. Second, in order to avoid the impact effects of particles with high velocities on the angle of repose, let the loose packing particles fall to a container under gravity up to reaching stable dense packing. Finally, the left and right wall of contalner are removed, the dense packing particles will collapse under gravity, at last, a stable sandpile can be obtained. In this simulation, the parameters and mass of particles are kept the same for each grain size distribution in order to have comparable conditions. The results indicate that repose angles of sandpile decrease significantly with particle size descending and approach to a constant. At the same time,the tests of sandpile formation for two groups with different size distributions have been completed, the results show that the angles of rest form test approximately approach to those of simulation.