DISCRETE ELEMENT SIMULATION OF SAND CONFINED COMPRESSION TEST BASED ON MatDEM
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摘要: 离散元法基于非连续介质力学理论，尤其适用于砂土等离散介质体的数值模拟研究。利用岩土体离散元模拟软件MatDEM的二次开发功能，研发了砂土侧限压缩试验三维离散元模拟器。对三个不同级配砂土试样进行了侧限压缩试验，并且进行了与之相对应的数值模拟，通过分析对比试验结果与数值模拟结果验证了所开发模拟器的有效性。模拟结果表明：离散元法可以很好地反应砂土压缩过程中的配位数变化；每个模拟样品中，粒径较小的单元受到较大的平均压力，导致平均位移较大；数值计算结果的主要误差是由离散元颗粒自身的泊松比引起的。研究突破了常规土力学研究方法的局限性，为今后岩土工程离散元模拟研究提供了参考。Abstract: Discrete element method is suitable for numerical simulation of discrete mesoporous media such as sand, because discrete element method is based on discontinuous medium mechanics theory. A 3D discrete element simulator for sand confined compression test was developed by the discrete element simulation software MatDEM. Confined compression tests for 3 different graded sands were carried out, and the numerical simulation matched with the test was carried out. The validity of the developed simulator was verified by the comparison between the test and numerical simulation results. The results show that DEM can well reflect the change of the coordination number in the compression process of sand; in each sample, the elements with smaller size are subjected to greater average pressure, which leads to a larger average displacement; the main error of numerical simulation was caused by the Poisson's ratio of the discrete element particle. This study overcomes the limitations of the conventional soil mechanics research methods, and provides a reference for the study of the discrete element simulation of geotechnical engineering in the future.
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Key words:
- sand /
- confined compression test /
- DEM /
- numerical simulation /
- error analysis
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图 1 离散元中Hertz接触模型示意图
Figure 1. Schematic diagram of the Hertz contact model in discrete element method
图 4 数值模拟与试验应力应变曲线对比
Figure 4. Comparison of stress and strain curves between the numerical simulation and the test
图 6 数值模拟中单元平均位移的变化
Figure 6. The variation of unit average displacement in numerical simulation
图 7 数值模拟中单元平均受力的变化
Figure 7. The variation of unit average force in numerical simulation
图 9 球形石英砂颗粒受压变形示意图
Figure 9. A schematic diagram of compression deformation of a spherical quartz sand particle
表 1 模拟与试验砂样物理参数对比
Table 1. Comparison of physical parameters of the simulated sand and the tested sand
砂样编号 类型 粒组/mm 总质量/g 各粒组质量比 孔隙比 单元数量/个 1号 试验 0.4~0.6/1~1.2 85 1:1 0.8303 模拟 0.4~0.6/1~1.2 1.002:1 0.8670 323750 2号 试验 0.4~0.6/0.6~0.8 86 1:1 0.8209 模拟 0.4~0.6/0.6~0.8 1:1 0.8670 403699 3号 试验 0.4~0.6/0.6~0.8/1~1.2 89 1:1:1 0.8121 模拟 0.4~0.6/0.6~0.8/1~1.2 1:1.024:0.983 0.8591 236192 
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表 2 模型微观力学参数
Table 2. Micromechanical parameters of the model
类型 法向刚度/(N/m) 切向刚度/(N/m) 断裂位移/m 抗剪力/N 摩擦系数 试算值 1.3139×106 4.1931×105 0 44.3733 0 解析值 1.1254×106 4.0193×105 0 39.9360 0
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