Experimental evaluation of a steel U-shaped embedded track for vibration and noise mitigation in metro line retrofit

This study evaluates a newly developed steel U-shaped embedded track system designed for vibration and noise mitigation in existing metro lines. The system enables rapid modular installation and provides a compliant polymer support layer for improved vibration isolation. Comprehensive before–after field measurements were conducted on rail and tunnel vibration, in-train noise, and building structure-borne noise. The peak rail acceleration decreased from 219 to 85 m/s 2 , and the peak tunnel-wall acceleration was reduced from 0.194 to 0.025 m/s 2 . and lowered indoor structure-borne noise by 4.9 - 6.1 dB(A). In-train A-weighted noise decreased by 4.1 - 5.1 dB(A). The results confirm that the proposed embedded track provides an effective and practical retrofit solution that meets relevant vibration and noise limits and significantly improves the environmental performance of existing metro lines.