Influence of Cyclic Stress Pulse Shapes on Filtration Behavior of Railway Subballast

Filtration behavior of subballast materials subjected to different cyclic stress pulse shapes at frequencies of 5 Hz and 10 Hz was investigated in the laboratory. Clayey silt was used as a base soil while graded crushed basalt was used as a filter. Rectangular, sinusoidal, and triangular cyclic stress pulse shapes having a stress range of 70–140 kPa were investigated for a piping ratio of 9. Turbidity, permeability, and change of pore water pressure within base soil were recorded over time as the number of stress pulse cycles increased. Results show that triangular and sinusoidal cyclic stress pulse shapes have a similar effect on the filtration behavior while the rectangular cyclic pulse shape had a slightly higher effect than triangular and sinusoidal stress pulse shapes. Based on this study, a piping ratio of 9 was found to be satisfactory for all cyclic stress pulse shapes at 5 Hz.