Explanations of anisotropic strength and fabric evolution in granular soils by DEM simulations and buckling failure theory
Explanations of anisotropic strength and fabric evolution in granular soils by DEM simulations and buckling failure theory
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DOI：
10.1080/17486025.2020.1755465
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发表时间：
2020-05
期刊：
影响因子：
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通讯作者：
Junxing Zheng;Hantao He;Zhaochao Li
中科院分区：
文献类型：
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作者：
Junxing Zheng;Hantao He;Zhaochao Li
摘要本研究旨在基于离散单元法(DEM)的模拟，对不同固有组构引起的颗粒土各向异性强度进行微观解释。土壤颗粒被模拟为椭球体(即块状球体)，以保持真实土壤颗粒的伸长分布，该分布是通过分析18个沙子中的90,000个颗粒而确定的。然后，通过限制颗粒的长轴取向，在12种不同的固有组构上制备了虚拟土样。对于每一种固有织物，在五个中间应力比值下模拟三轴试验，总共产生60个DEM模拟。基于模拟结果，研究了各向异性剪切强度与织物演化之间的关系。对于特定的固有结构，Lade的各向同性破坏理论可以用来描述峰值和临界状态下的剪切强度和八面体接触法向结构系数。介绍了结构工程学中的屈曲破坏理论，用来解释在实验室试验和模拟中观察到的颗粒土的各向异性强度和织物的评价。当荷载与织物方向的夹角从零增加到90度时，土柱的概念宽度减小，从而导致较小的屈曲破坏荷载，从而导致散体土的抗剪强度较小。
ABSTRACT This research aims to discover a micro explanation of anisotropic strength of granular soils caused by different inherent fabrics based on the discrete element method (DEM) simulations. Soil particles are simulated as ellipsoids (i.e., clumped spheres) to preserve the elongation distributions of real soil particles that are determined by analysing 90,000 particles from 18 sands. Then, virtual soil specimens are prepared at 12 different inherent fabrics by restricting the particle long axis orientations. For each inherent fabric, triaxial tests are simulated at five intermediate stress ratio values, resulting in a total of 60 DEM simulations. The relationships between anisotropic shear strength and fabric evolution are investigated based on simulation results. For a specific inherent fabric, Lade’s isotropic failure theory can be used to describe shear strengths and octahedral contact normal fabric factors at peak and critical states. A buckling failure theory from structural engineering is introduced to explain the anisotropic strength of granular soils and fabric evaluations observed in laboratory tests and simulations. As the angle between loading and fabric direction increases from zero to 90 degrees, the conceptual widths of soil columns decrease, leading to the smaller buckling failure loads and therefore the smaller shear strength of granular soils.