Experimental study on vibration characteristics of the floating slab with under-slab polyurethane mats considering fatigue loading effect

Under-slab polyurethane mats (USPM) are commonly recommended as a reliable vibration-damping measure in metro traffic. Since the design speed and axle load of the urban rail transit lines are different from those of the ordinary speed lines, the vibration characteristics of polyurethane mat floating slab track (PMFST) during long-term service need to be studied furtherly. This study investigated the vibration characteristics and transmission law of PMFST during the fatigue process and compared it with ordinary track (OT), which is the same as PMFST but without the under-slab mat using full-scale indoor laboratory models. The results show that: 1). Under -sleeper subsystem (including track slab, USPM, and foundation) experienced hardening during the fatigue process. The static and dynamic stiffness change rates after 5 million cycles were 6.4% and 10.8%; The overall change rates of static and dynamic stiffness after 10 million cycles were 8.7% and 12.8%. 2). The time-domain analysis showed that PMFST could significantly reduce the vibration duration and ground acceleration; Fatigue loading accelerated the degradation of the USPM, reducing the capacity of dissipating energy. 3). The slab -ground subsystem was the main attenuation section for PMFST, which could significantly reduce the energy transfer ratio. Compared with OT, PMFST performed better in dissipating the vibration energy along the lon-gitudinal direction; However, fatigue loading would aggravate the vibration level. Overall, the vibration levels of PMFST (0 million, 5 million, and 10 million) can be reduced by 14.4 dB, 13.5 dB, and 10.9 dB, respectively.