Effective medium theory and discrete-element method (DEM) simulations of smooth spheres both fail to correctly capture the small-strain stiffness of soil. The inability of the latter to capture small-strain stiffness can be overcome by adopting a rough-surface contact model, which includes the effect of asperity deformation. Hertzian spheres are commonly used in DEM which neglect the Poisson effect – that is, the lateral extension of a sphere orthogonal to an applied load. The hypothesis investigated in this paper is that this omission contributes to the inability of smooth-sphere DEM simulations to correctly capture the stress dependence of the elastic moduli of soil. This hypothesis was investigated using the finite-element method. At low-to-moderate confining stresses, the Poisson effect has little influence on the response. The Poisson effect becomes significant only at confining stresses on the order of 100 MPa, using parameters appropriate for a silica sand: stresses at which massive particle crushing would be expected. At lower stresses, rough-surface contact models remain the most justifiable way to match the stress–stiffness response measured in laboratory testing using DEM simulations.

中文翻译：

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泊松效应对土弹性模量应力依赖性的影响

光滑球体的有效介质理论和离散元方法 (DEM) 模拟均未能正确捕捉土壤的小应变刚度。后者无法捕捉小应变刚度可以通过采用粗糙表面接触模型来克服，该模型包括粗糙变形的影响。赫兹球通常用于 DEM，它忽略了泊松效应——即与施加载荷正交的球的横向延伸。本文研究的假设是，这种遗漏导致光滑球 DEM 模拟无法正确捕捉土壤弹性模量的应力依赖性。使用有限元方法研究了这个假设。在低到中等的围压下，泊松效应对响应的影响很小。泊松效应仅在限制应力为 100 MPa 的情况下变得显着，使用适用于硅砂的参数：预计会出现大量颗粒破碎的应力。在较低应力下，粗糙表面接触模型仍然是匹配在实验室测试中使用 DEM 模拟测量的应力-刚度响应的最合理方法。