Estimation of the dynamic stiffness of railway ballast over a wide frequency range using the discrete element method

•High-frequency ballast dynamic stiffness is determined through impact experiments.•Contact characterization for discrete element method (DEM) modeling of the ballast.•DEM model for determining the ballast's dynamic stiffness at high frequencies.•Examine, using force networks, the impact of ballast confinement on the dynamic behavior of ballast.•Steady increase in dynamic stiffness with frequency, particularly above 100 Hz is observed.•Influence of preload on the measurement of ballast dynamic stiffness.