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 behavior (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 embedding agglomerates of spheres (clumps) into discrete simulations. The present work focuses on obtaining surface mesh of particle geometry using different imaging techniques and comparing their behavior with clumps. Preliminary results suggests that the clumps tend to provide higher sliding resistance when compared to polyhedral particles due to unrealistic concave features of the clumps. Further simulations will be carried out to calibrate individual particle breakage characteristics and model the bulk behavior under different loading conditions. Finally, the study relates the evolution of internal variables due to breakage with the macroscopic response of granular assembly. These relationships can be further used to enrich the continuum based constitutive laws.