This note evaluates the ability of a combined discrete–finite-element approach to replicate the experimental response of a dry sand under triaxial compression. The numerical sample was created by virtualising the fabric of a Martian regolith-like sand sample obtained from an in situ test using X-ray micro computed tomography; physical properties of the grains obtained from laboratory data were used as input. The boundary and contact conditions were defined according to the experimental test. A key feature of the model is the use of deformable thin-shell elements to represent the numerical membrane, which allows for a realistic failure mode and volumetric deformation. The macroscopic response of the numerical simulation is shown to compare well with the experiment. The contact regions are identified based on their ability to transmit stress and the evolution of the contact normals is shown to correlate well with the macro stress evolution. The computed stress fields within each grain are used to identify the load-bearing grains in the assembly, contributing new insights beyond the commonly reported force chains.

中文翻译：

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土行为的微观有限元模型：三轴压缩下砂土的实验评估

本说明评估了组合的离散有限元方法在三轴压缩下复制干砂的实验响应的能力。数值样本是通过虚拟化从火星的长石状砂样的织物创建的，该样品是使用X射线计算机断层扫描从原位测试获得的；从实验室数据获得的谷物的物理性质用作输入。边界和接触条件根据实验测试确定。该模型的一个关键特征是使用可变形的薄壳元件来表示数字膜，从而可以实现实际的破坏模式和体积变形。结果表明，数值模拟的宏观响应与实验比较良好。根据接触区域传递应力的能力来确定接触区域，并且显示接触法线的演变与宏观应力的演变具有很好的相关性。每个晶粒内计算出的应力场用于识别装配体中的承重晶粒，为通常报告的力链之外的问题提供新的见解。