DEM simulation of shear vibrational fluidization of granular material
DEM simulation of shear vibrational fluidization of granular material
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DOI：
10.1007/s10035-018-0844-8
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发表时间：
2018-09
期刊：
影响因子：
2.4
通讯作者：
Zhihua Zhang;Yi-fei Cui;D. Chan;K. Taslagyan
中科院分区：
文献类型：
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作者：
Zhihua Zhang;Yi-fei Cui;D. Chan;K. Taslagyan
干燥颗粒材料的流化是当在振动期间施加足够的能量时从固态到液态的转变。这种行为是重要的，因为它是密切相关的岩土结构在地震期间的变形。科学上的挑战在于理解在整个剪切过程中应变局部化与流化区的关系。尽管颗粒材料在流化过程中的力学行为很重要，但传统的直剪试验不能很容易地表征它。本文首先建立了二维离散元模型，定义了干燥颗粒物料的剪切振动流态化，并采用离散元方法对颗粒物料在剪切振动载荷作用下的直剪试验进行了数值模拟。通过数值模拟得到了峰值、残余和振动残余抗剪强度包络线。根据振动前观察到的体积应变变化，在上部剪切盒中确定了三个不同的区域。在振动过程中，流化发生在三个区域的特点，剪切应力，孔隙度，体积应变，配位数下降到相对较低的值。在振动过程中，材料变得比临界状态更致密，应变局部化得到缓解。材料在剪切区的致密化导致材料的强化，这增加了振动后的剪切阻力。此外，进行了2D和3D模拟的比较。结果表明，颗粒在三维模拟中沿离面方向的运动使剪切应力更加平滑，与实验结果更加一致。
Fluidization of dry granular material is the transition from a solid state to a liquid state when sufficient energy is applied during vibration. This behavior is important because it is closely related to deformations of geotechnical structures during an earthquake. The scientific challenge lies in the understanding on how strain localization is related to the fluidization zone during the entire shearing process. Despite the importance of the mechanical behavior of granular material during fluidization, it cannot be easily characterized using traditional direct shear test. In this paper, 2D DEM model is firstly conduct, shear vibrational fluidization is defined for dry granular material, and the discrete element method has been used to simulate the direct shear test on granular material under vibrational loading during shearing. The peak, residual and vibro-residual shear strength envelopes have been obtained from the numerical simulations. Three distinct zones have been identified in the upper shear box based on the observed changes in volumetric strain before vibration. During vibration, fluidization occurs in the three zones with the characteristics that the shear stress, porosity, volumetric strain, and the coordination number drop to relatively lower values. During vibration, material becomes denser than the critical state, and strain localization has been relieved. Densification of the material at the shear zone leads to a strengthening of the material which increases the shearing resistance after vibration. Furthermore, a comparison of the 2D and 3D simulations is performed. Results reveal that the motion of particles in the out-of-plane direction in the 3D simulations lead to smoother shear stress and more consistent with the experimental result.