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DEM simulation of shear vibrational fluidization of granular material

机译：颗粒材料剪切振动流化的DEM模拟

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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.
机译：当在振动过程中施加足够的能量时，干粒状材料的流化是从固态到液态的过渡。此行为很重要，因为它与地震期间岩土结构的变形密切相关。科学的挑战在于对整个剪切过程中应变局部化与流化区的关系的理解。尽管在流化过程中粒状材料的机械行为很重要，但使用传统的直接剪切试验无法轻易地对其进行表征。本文首先建立了二维DEM模型，定义了干燥粒状材料的剪切振动流化状态，并采用离散元法模拟了剪切过程中振动载荷下颗粒状材料的直接剪切试验。峰值，残余和振动残余剪切强度包络已从数值模拟中获得。根据观察到的振动前体积应变的变化，在上部剪切箱中确定了三个不同的区域。在振动期间，在三个区域中发生流化，其特征在于剪切应力，孔隙率，体积应变和配位数下降到相对较低的值。在振动期间，材料变得比临界状态致密，并且应变局部化得到缓解。材料在剪切区的致密化导致材料的增强，这增加了振动后的剪切阻力。此外，进行了2D和3D仿真的比较。结果表明，在3D模拟中，粒子在平面外方向上的运动导致剪切应力更平滑，并且与实验结果更加一致。

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