## 4 Discussion  
Existing research suggests relatively simple analysis methods for steel-spring-floating slab tracks. In this study, the vibration responses of rails, track beds and tunnel walls of steel-spring-floating slab tracks and ordinary monolithic tracks under straight and curved conditions are compared by using a variety of signal processing and analysis methods. According to the results of the spectral (RMS) analysis, the frequency response of the tunnel wall in the steel-spring-floating slab track section is significantly reduced. Comparing Figure 15a with Figure 15b, it can be seen that compared with the ordinary monolithic track-tunnel-wall-acceleration amplitude spectrum in the straight line segment, the ordinary monolithic track-tunnel-wall-vibration acceleration amplitude spectrum in the curved segment has more peak points, and is larger in magnitude. This shows that the wheel-rail vibration in the curved segment is more complicated, which results in the phenomenon that more peak points appear in the acceleration spectrum of the ordinary monolithic track tunnel wall. For the above phenomenon, the steel-spring-floating slab track has a good reduction effect on these peak points, so it can ensure the vibration damping effect in the curve segment. Comparing the frequency-division vibration level curves in Figure 17, it can be seen that although the frequency-division vibration level curves of the rail and track bed are different in value, their shapes are basically the same. The attenuation of the sub-frequency vibration level of the steel-spring-floating slab track transmitted from the rail to the track bed is small. The reason is that the bottom of the steel-spring-floating slab track is suspended, and its restraint is less than that of the ordinary monolithic track, so the vibration effect is more significant. However, because the bottom of the ordinary monolithic track is fully constrained by rigidity, it is easier to transmit the vibration to the tunnel wall under the action of the dynamic load of the train, and the transmission capacity of high-frequency vibration is stronger, which leads to the similar frequency-division vibration level between the track bed and the tunnel wall of the ordinary monolithic track, in which the curves are closely spaced in the high-frequency range. Therefore, comparing the above phenomena, it can be seen that in the design of steel-spring-floating slab tracks, in order to limit the vibration of the track bed, it is necessary to appropriately increase the restraint at the bottom of the track bed, increase the number of vibration isolators, and appropriately increase the stiffness value. For different line conditions, the frequency-division vibration level at the high frequency of the curved segment is significantly larger than that of the straight line segment, and the ordinary monolithic track and tunnel wall at steel-spring-floating slab track acceleration frequency-division vibration levels of the curved segment are both the maximum  
Figure 24: Comparison of \(Z\) vibration levels of track components under different line conditions. values near 5000 Hz, which shows that the setting of the curve segment will lead to aggravated vibration of the tunnel wall at high frequency. In terms of vibration transmission, the vibration transmission characteristics of the rails, track bed and tunnel walls of the steel-spring-floating slab track and ordinary monolithic track have obvious field characteristics (Figure 22). Comparing the rail-track transfer coefficient curves of the straight line segment and the curved segment, it can be seen that when passing through the curved segment, the rail-track bed transfer coefficient curves of the ordinary monolithic track and the steel-spring-floating slab track both show a new peak point at 791-1455 Hz. They are located at 1250.01 Hz and 976.56 Hz, respectively, and the transfer coefficient amplitudes are 0.233 and 0.915.