## 5 Conclusions  
By designing a vibration test scheme for subway lines, the vibration tests were carried out on the cumulative four working conditions of ordinary monolithic track and steel-spring-floating slab track under different line conditions (straight line and curved segment) with similar speeds. The vibration responses of rail, track bed, and tunnel wall under real train loads under four working conditions were mainly studied. Based on various time-frequency analysis methods, the vibration of track components under different working conditions was comprehensively analyzed, and the following results were obtained:  
(1) According to the time domain, frequency domain and Z vibration level analysis results, it is shown that steel-spring-floating slab track can significantly reduce the acceleration response of the tunnel wall, and all kinds of vibration indicators at the tunnel wall are larger for the ordinary monolithic track, indicating that steel-spring-floating slab tracks can significantly reduce the impact of subway trains on the surrounding environment. (2) By comparing the time-frequency curves of rail, track bed, and tunnel walls, it can be seen that under the action of train loads, the dynamic responses of the rail under the four working conditions are relatively close, where the steel-spring-floating slab track is slightly larger than that of the ordinary monolithic track, and the acceleration steel-spring- floating slab track of the track bed is significantly larger than that of the ordinary monolithic track. (3) In the case of two different lines, the driving speed of the curved segment is lower than that of the straight line segment, but the vibration response generated by it is significantly larger than that of the straight line segment, and each frequency band will generate more peak points, and the high-frequency vibration will be more severe. At the same time, the comparison of the two track structures shows that the vibration of the ordinary monolithic track is more easily affected by the line conditions. (4) According to the frequency-response transfer analysis between the track components, it can be seen that the rail-track bed vibration transfer rate of the steel-spring-floating slab track is significantly greater than that of the ordinary monolithic track, while the vibration transfer rate of its track bed-tunnel wall is significantly smaller than that of the common integral-track bed track. It shows that for the steel-spring-floating slab track, one needs to pay more attention to the vibration control of its track bed in the process of use to ensure the safety and stability of subway trains. Meanwhile, the countable effect and possible impact on the optimization design of the steel-spring-floating slab track are put forward as follows:  
(1) At present, the research methods for the dynamic characteristics of the steel-spring-floating slab track are relatively simple, and a deeper exploration of the dynamic characteristics of the steel-spring-floating slab track is carried out to further reveal the vibration reduction and transmission mechanism of the steel-spring-floating slab track, and then optimize the track structure and the design of the vibration isolator. (2) In this study, a variety of time-frequency analysis methods were used to compare the dynamic characteristics of the cast-in-place steel-spring-floating slab track under different line conditions, and further reveal the vibration characteristics of the cast-in-place steel-spring-floating slab track in the actual vehicle-operating environment. At the same time, it can be seen that the vibration in the curved section is more random. (3) Therefore, it is recommended to limit the speed of subway trains in curved segment, and take more limiting measures for steel-spring-floating slab track, such as adding lateral limit vibration isolators to control the dynamic response of steel-spring-floating slab track in a curved segment.