Polyhedron

Engineering

SPHERES

Materials science

Shear (geology)

Computer science

Statistical physics

Geology

Oceanography

Physics

Mathematics

Astronomy

Ballast

Geometry

Particle (ecology)

Composite material

Engineering drawing

Discrete element method

Mechanics

Friction coefficient

International Journal of Rock Mechanics and Mining Sciences

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.

Modelling real particle shape in DEM: a comparison of two methods with application to railway ballast