Particle shape and its importance to Discrete Element Modeling in the context of railway ballast simulation

Resumo

Computational tools may be helpful to understand the railway ballast mechanical behavior. In the
context of the Discrete Element Method (DEM), a numerical simulation may be performed considering different
grain shapes and parameters to represent the actual ballast. It is well-known that modeling faceted aggregates
(polyhedral) provides interlocking between particles. This may avoid rolling movements. On the other hand,
employing spherical particles to represent non-spherical grains may neglect the physical expected rolling
resistance. In this paper a shear box test simulation using DEM was investigated, considering distinct shapes of
ballast aggregate. The macroscopic mechanical behavior will be addressed for each case. It will be considered
realist railway ballast retained at sieves of 25 mm, 38 mm and 50 mm. An inexpensive laser scanning technique is
also employed with realistic grains, in order to incorporate their shape into the DEM. An extensive parametric
study was conducted exploring the influence of the particle shape (spheres, basic polyhedral and scanned particles),
in order to find the best compromise way to simulate a desirable scenario, from the engineering point of view.