Research on Under Sleeper Pads for reducing vibrations in railway transport

This study investigates the vibration isolation performance of under-sleeper pads (USPs). A reduced-scale laboratory track model was used, with simultaneous acceleration and displacement measurements at the sleeper substitute and at the subgrade surrogate. Five USP variants differing in stiffness and bottom-surface geometry were tested against a baseline configuration without a pad under harmonic excitation at 3, 5, 10 and 20 Hz (three repetitions per case). Vibration transmission was quantified using transfer functions expressed as the ratio of subgrade-to-block responses for RMS acceleration and peak-to-peak displacement. The results show a consistent trade-off: installing a USP increases the motion of the sleeper substitute (higher block RMS acceleration and displacement) due to added compliance, while reducing vibration levels at the subgrade surrogate. The attenuation strongly depends on pad stiffness and geometry, indicating that both material properties and surface design significantly influence vibration transmissibility. Softer and corrugated variants yielded the lowest transfer-function values and the highest vibration isolation. Based on the quantitative ranking, one optimized pad variant (characterized by unit static stiffness ≈ 0.12 N/mm³ and a corrugated contact surface) was selected for planned in-track verification on the PKP PLK network (Polish Railway Lines).