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-  2018 

Analysis of shear behavior of sand based on elastic boundary simulation of discrete element method

Keywords: 道路工程,砂土,离散元,弹性边界,剪切带,应变局部化
road engineering
,sand,DEM,flexible boundary,shear band,strain localization

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Two dimensional discrete element method (DEM) was used to carry out numerical biaxial test to study the shear behavior of sand. By abstracting the flexible wrapping effect of rubber membrane on sand samples in laboratory test as the specified normal pressure acting on boundary particles of the sample, the conventional discrete element numerical biaxial test was improved. The improved discrete element biaxial test could effectively simulate the lateral inhomogeneous deformation of sand samples after shear failure in laboratory test, and parameter studies were carried out to clarify the effect of confining pressure and particle friction coefficient on the shear behavior of sand. Moreover, the formation process and corresponding mechanism of shear band were investigated from microscopic perspectives. The results show that strain softening and shear shrinkage of sand increase with the increase of confining pressure, while the shear dilatancy decreases with the increase of confining pressure. The deformation modulus of sand increases with the increase of confining pressure, but the increase is not obvious. The residential strength of sand seems not to be affected by confining pressure, while the peak strength is obviously affected by confining pressure. The peak strength and corresponding axial strain increase with the increase of particle friction coefficient. The contribution of confining pressure and particle friction coefficient to the peak strength of the sample is limited. Soil particles on both sides of shear band move in adverse directions, and the contact force chain is distributed mainly along the loading direction, showing unloading characteristics. Soil particles within shear band are staggered, and the angular displacement is larger around its centroid, and the contact force chain deflects horizontally, resulting in obvious strain localization. The strain localization occurs at the center of the specimen initially, and then quickly through the whole specimen, and the specimen reaches the peak strength. In the shear band, the particle


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