Particle shape has a strong effect on the mechanical response of coarse soils. This has been usually observed examining specimen-scale or engineering-scale responses, which are the sum of many microscale interactions. In this work we observe the effects of particle shape directly at the microscale level. X-ray tomography (μ-CT) of two sand specimens is exploited to measure three-dimensional particle shape descriptors but also to track individual particle motions during triaxial compression. A discrete digital volume correlation algorithm is employed to track the motion of individual grains (around 50,000 for each sand specimen) during the test and measure, with good precision, their cumulated displacements and rotations. The specimens examined failed in a clearly localised shear mode. Advantage is taken of this to obtain data relevant for very different kinematical regimes: one uniform and more constrained and the other close to critical state. A direct comparison between the shape and kinematic databases shows to what degree particle shape descriptors are related to observed kinematics. It appears that true sphericity is a good predictor of upper bound rotational restraint.

颗粒形状对粗糙土壤的机械响应有很大影响。通常可以通过检查标本规模或工程规模的响应来观察到这一点，这些响应是许多微尺度相互作用的总和。在这项工作中，我们直接在微观水平上观察了颗粒形状的影响。利用两个沙子样本的X射线断层扫描（μ-CT）来测量三维颗粒形状描述符，还可以跟踪三轴压缩过程中单个颗粒的运动。在测试和测量过程中，采用离散的数字体积相关算法来跟踪单个颗粒的运动（每个沙粒大约为50,000个），并以很高的精度测量它们的累积位移和旋转。检查的样品在明显的局部剪切模式下失效。利用这一优势来获得与非常不同的运动方式相关的数据：一种是统一且受限制的，另一种接近临界状态。形状和运动学数据库之间的直接比较表明，颗粒形状描述符在多大程度上与观测到的运动学相关。似乎真实的球形度是上限旋转约束的良好预测指标。