This paper presents a discrete-element method simulation of mini-triaxial tests on a sand with realistically shaped grains. It compares the results with physical experiments at multiple length scales, including the macroscopic sample length scale and the particle scale. A series of image-processing techniques were utilised to binarise, segment and label the raw data in images obtained from the mini-triaxial test. The images were obtained using an X-ray synchrotron radiation scanner. A spherical harmonic analysis was used to filter the image data and to reconstruct the natural particle morphology. Two parameters, these being the radius ratio of the smallest to largest sphere

$\rho$

and a characteristic distance

$\varphi \in [0^{\circ },180\text{°}]$

within the multisphere clump method, were chosen to represent the realistic particle morphology, balancing accuracy against computational cost. A one-to-one discrete-element model, where every particle in the physical experiment has its own numerical twin, was constructed. The discrete-element model was contained by a numerically generated flexible membrane allowing free deformation of the specimen under a prescribed confining stress, as in a physical triaxial test. Finally, attention was given to particle scale properties and their influences on the mechanical response of the discrete-element model. For a given strain rate it was found that shear modulus and friction coefficient affect the initial stiffness, the peak load and the dilation significantly. This study, and the simulation results within it, demonstrate that the proposed modelling approach is capable of reproducing macroscopic (e.g. stiffness, deviatoric stress response and volumetric response) and particle-level (e.g. displacement, rotation and branch vector orientation) behaviours that are very similar to what occurs within physical experiments, validating the effectiveness of the proposed one-to-one mapping technique.

中文翻译：

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基于砂粒一一映射的微型三轴试验DEM建模

本文介绍了对具有真实形状颗粒的沙子进行微型三轴试验的离散元方法模拟。它将结果与多个长度尺度的物理实验进行比较，包括宏观样品长度尺度和粒子尺度。一系列图像处理技术被用来对从微型三轴测试获得的图像中的原始数据进行二值化、分割和标记。这些图像是使用 X 射线同步辐射扫描仪获得的。球谐分析用于过滤图像数据并重建自然粒子形态。两个参数，它们是最小球体与最大球体的半径比

$\rho$

和特征距离

$\phi \in [0^{\circ },180\text{°}]$

在多球团块方法中，被选择来代表现实的粒子形态，平衡计算成本的准确性。建立了一对一的离散元模型，其中物理实验中的每个粒子都有自己的数值孪生。离散元模型包含在数值生成的柔性膜中，允许试样在规定的围压下自由变形，如在物理三轴试验中。最后，关注粒子尺度特性及其对离散元模型机械响应的影响。对于给定的应变率，发现剪切模量和摩擦系数显着影响初始刚度、峰值载荷和膨胀。这项研究以及其中的模拟结果，