Breakage and shape analysis of ballast aggregates with different size distributions
Particle breakage usually alters the size and shape of ballast aggregates, which significantly influences the long-term performance of rail tracks. This study reports an investigation on the breakage and shape characteristics of ballast aggregates subjected to monotonic and cyclic triaxial tests with two different load frequencies. The results show that particle breakage is not only influenced by the particle size distribution but also by the relative density. Breakage indices defined by breakage potential and grading entropy fail to characterize the breakage extent of ballast with multiple initial particle size distributions, while the Marsal breakage index exhibits a general decrease with increasing coefficient of uniformity for ballast with similar relative densities. Higher breakage extent is observed in ballast subjected to a higher load frequency. Particle shape varies with load frequency because of breakage. A slightly higher value of each shape index is observed for ballast subjected to a higher load frequency, implying that ballast aggregates become increasingly regular with the increase of load frequency.