Performance research and effect evaluation of a high-grade damping fastener in subway line

Abstract

In recent years, some subway lines have been upgraded with vibration and noise reduction technology. As the only component connecting rail and sleeper, the fastener system has been the primary solution to vibration and noise reduction in subways. However, due to the mismatch between the structure design and material selection of the fastener system, the performance decay and aging failure of the fastener elastic pad occurred in less than one year of service in the line. In this paper, we choose a high-grade damping fastener with low vertical and high lateral stiffness as the research object, and explore the design method of fastener system to control the failure of stiffness aging and rail wear. Following that, theoretical analysis and experimental research are conducted on structural components of the higher damping fastener. The main conclusions are as follows: First, the stiffness of the damping fastener is adjustable in real time. By adjusting the nut installation height, optimizing the thickness of the elastic pad under the plate, and alerting the lateral block contact angle can change the vertical stiffness of fastener system by 19.4 %, 27.1 %, and 28.6 %, respectively. Second, before the line replacement, the rail roughness under the Egg type damper (Egg damper) is increasing exponentially. After replacing with the ZK type high-grade damping fastener (ZK fastener), the average roughness of high and low rails decreases at a rate of −0.3 dB/month. Third, hammering test results indicate that the vertical support stiffness of the ZK fastener is significantly lower than that of the Egg damper, while the lateral stiffness is 2.55 times greater than that of the Egg damper. Fourth, compared to the Egg damper before replacement, the maximum vertical vibration at the tunnel wall with the ZK fastener is reduced by 6.9 dB, and the dynamic twisting at the rail head is only half of the original. Application of the new damping fastener system in subway line replacement over the past two years not only reflects a clever stiffness design principle but also demonstrates good track stability, making it a preferred high-grade damping modification measure for controlling subway vibration and noise.