Bounding surface model for ballast with additional attention on the evolution of particle size distribution
Particle size distribution significantly influences the mechanical response of the ballast under low confining pressure. However, particle breakage usually occurs and unfavorably degrades the particle size distribution of the ballast when sufficient load is applied. To model the triaxial stress-strain behavior and its associated evolution of particle size distribution of the ballast, a specific bounding surface model is proposed. The proposed model is based on the traditional bounding surface plasticity and a modified particle breakage index, which correlates the initial gradation and the ultimate gradation together with the current gradation. Simulation of the experimental results from the triaxial compression tests shows that the proposed model can predict the strain softening and volumetric expansion of the ballast under relatively lower confining pressure. It is also able to simulate the strain hardening and volumetric compression of the ballast under relatively higher confining pressure. Most importantly, the proposed approach was observed to have a great potential in predicting the evolution of the particle size distribution of the ballast.