The three-dimensional discrete element method (DEM) was employed to investigate the combined effects of inherent and stress-induced anisotropy of granular materials. The particles were modeled following real particle shapes. Both isotropic and inherently anisotropic specimens were prepared, and then true triaxial numerical tests were conducted using different intermediate principle stress ratios (b). The results indicate that the oriented particles in the anisotropic specimens form strong contacts in their long axis direction in the early stages of shearing, which restrains the contraction of the specimens. As the strain increases, the oriented particles start to rotate and slide, which results in shorter contraction stages and fewer number of interparticle contacts with peak values compared to the isotropic specimens. In addition, the increase in b values aggravates the rotating and sliding of particles in the inherently anisotropic specimens and restrains the contraction of the granular and the increase of contact forces. As a result, the inherent anisotropy reduces the effects of stress-induced anisotropy on the mechanical behavior of granular materials.

中文翻译：

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用三维离散元方法研究固有和应力各向异性对颗粒材料力学行为的综合影响

三维离散元方法（DEM）用于研究颗粒材料固有和应力诱发的各向异性的综合影响。按照真实的粒子形状对粒子进行建模。制备了各向同性和固有各向异性的试样，然后使用不同的中间主应力比进行了真正的三轴数值试验（b）。结果表明，各向异性试样中的取向颗粒在剪切的早期阶段沿长轴方向形成强接触，从而抑制了试样的收缩。随着应变的增加，与各向同性样品相比，定向粒子开始旋转和滑动，这导致更短的收缩阶段和更少的具有峰值的粒子间接触。另外，b值的增加加剧了固有各向异性样品中颗粒的旋转和滑动，并限制了颗粒的收缩和接触力的增加。结果，固有的各向异性减小了应力引起的各向异性对粒状材料的机械性能的影响。