The mechanical behavior of rock-based aggregates is of great interest as they dictate the stability of civil structures such as railway tracks, rockfill dams, stone columns, shore protection etc. The crushed stones are often being subjected to high cyclic/ monotonic loads especially the ballast layer, being the load transferring component between the track and the subgrade, plays a crucial role in transmitting the loads safely to the subgrade. The particle degradation disrupts the structural performance of the layer thereby increasing the costs associated with track maintenance. The degradation is a multi-scale phenomenon that originates at the contact level and affects the performance at the design scale. The macroscopic behaviour (strength and deformation characteristics) depends on the micro-scale variables (morphology, fabric, coordination number) for these crushable granular materials. The morphological changes of the crushed stones due to cyclic loads impacts negatively on the contact anisotropy resulting in the dissipation of assembly strength. Even though extensive studies had been carried out to understand the degradation behavior at continuum level, a contact level perspective especially considering realistic morphologies needs to be explored.
A particle-based numerical technique known as Discrete Element Method (DEM), was proven to be an effective tool for studying the underlying physics of granular materials. In the past decade, simple shapes such as discs/ spheres were used to model granular systems, but this approximation fails to represent the realistic behavior of rock clasts and their degradation characteristics. Many studies have come up with strategies to overcome this limitation by acquiring the realistic morphologies from X-ray CT images/ laser scanners and embedding into discrete simulations. Further, particle breakage strategies such as Fragment Particle Replacement (FRM), Bonded Particle Method (BPM) and coupling DEM with FEM are also implemented to simulate particle damage. The seminar reviews quantification and evolution of micro-variables (morphology, fabric anisotropy, coordination number) when rock-based aggregates are subjected to different loading conditions. The relations between contact anisotropy and macroscopic stress in a granular assembly derived from simulations aided with image-based experiments are reviewed. These relationships can be further used to enrich the continuum based constitutive laws.