Micro-analysis of Ballast Angularity Breakage and Evolution by Monotonic Triaxial Tests

Ballast particle angularity breakage may occur even under relatively lower stress compared with breakage, which leads to ballast degradation and fines accumulation. The degradation evolution and results have huge influence on potential recycling, reusable, and renewable design and operations. In the paper, the ballast angularity reduction under monotonic triaxial tests was studied, with different confining pressure including 10, 30 and 60 kPa. A simplified DEM model was developed to investigate the ballast particle angularity reduction and fines accumulation. The ballast particles were modeled by irregular clusters, where the small spheres were attached to the center sphere to simulate the angularity, as well as the fines after fracture. Results in DEM present a good coincidence with test data, and the presented irregular cluster was able to capture the degradation behavior of ballast angularity subject to loading. This paper demonstrates that ballast angularity reduction and fines accumulation increases with confining pressure increasing, which plays an important role in governing ballast degradation and recycling.