Two different methods for the modelling of real particle shape in 3D DEM simulations are assessed in this paper. The first method uses overlapping spheres (clumps), while the second uses a block defined as a closed and convex polyhedron. The two methods are applied to the modelling of triaxial tests on a railway ballast. The macroscopic responses obtained with the two methods are compared, and it is observed that with clumps a higher shear strength, closer to the experimental response, can generally be achieved. A micromechanical analysis is also carried out to highlight how the modelled particle shape affects the mechanics, and consequently explain the difference in the macroscopic response. It is observed, in particular, that a key feature of real particle shape is concavity, that plays an important role in the mechanics of a granular assembly. Finally, the combined effect of particle shape and interparticle friction coefficient on the shear strength is assessed. This confirms that even for real (angular) shapes, peak strength increases with interparticle friction, while critical state strength first increases and then tends to saturate above a certain interparticle friction.

本文评估了在 3D DEM 模拟中对真实粒子形状进行建模的两种不同方法。第一种方法使用重叠球体（团块），而第二种方法使用定义为封闭凸多面体的块。这两种方法应用于铁路道碴三轴试验的建模。将两种方法获得的宏观响应进行了比较，观察到，对于团块，通常可以获得更高的剪切强度，更接近实验响应。还进行了微观力学分析，以突出建模的粒子形状如何影响力学，从而解释宏观响应的差异。特别是观察到，真实颗粒形状的一个关键特征是凹度，它在颗粒集合体的力学中起着重要作用。最后，评估了颗粒形状和颗粒间摩擦系数对剪切强度的综合影响。这证实了即使对于真实的（有角的）形状，峰值强度也随着颗粒间摩擦而增加，而临界状态强度首先增加，然后趋于饱和，超过一定的颗粒间摩擦。