The influence of particle shape and loading waveform on the dynamic properties of base materials in high-speed railway slab tracks: A discrete element analysis

This study investigates the dynamic behavior of base materials in high-speed railway slab tracks using a combined experimental and numerical approach. Cyclic triaxial tests under sinusoidal loading were performed to calibrate Discrete Element Method (DEM) simulations. The effects of particle shape (high, medium, low aspect ratios) and loading waveforms (sinusoidal, triangular, rectangular) at varying frequencies were evaluated under drained conditions. Results show that higher loading frequencies-simulating faster train speeds-increased shear modulus, while lower frequencies enhanced energy dissipation and reduced stiffness, particularly at low shear strains. Rectangular loading produced greater stiffness and energy dissipation compared to sinusoidal and triangular forms. Power-law equations were developed to predict shear modulus and damping ratio based on shear strain, confining pressure, void ratio, particle shape, loading frequency and waveform. Micromechanical analysis showed that high-aspect ratio particles under rectangular loading exhibited the highest coordination numbers, contact forces, displacement, and rotation. Although higher aspect ratio intensified contact forces, it had a limited effect on the spatial distribution of force chains. These findings offer valuable insights for the design and performance evaluation of sub-ballast and base layers under dynamic loading, particularly in cases where in-situ testing is impractical.