## 3 Test Data Analysis  
### Time Domain Analysis  
#### 3.1.1 Time-Domain Curve Analysis  
During the test, the vibration of the environment around the tunnel will generate a certain amount of clutter, and the acceleration sensor at the tunnel wall has high accuracy, so it is very susceptible to the influence of small external vibrations. Therefore, in order to eliminate the influence of clutter on the experimental analysis, it is necessary to perform noise reduction processing on the collected signals. According to the analysis of the reference [19], the wavelet threshold denoising has a good noise reduction effect on the vibration test data, so it is eliminated to reduce the noise in the test process.  
Based on the vibration test data after noise reduction, in order to compare and study the vibration characteristics of the steel-spring-floating slab track relative to the ordinary monolithic track under different line conditions, time-domain analysis of the accelerations of rail, track bed, and tunnel walls for the ordinary monolithic track and the steel-spring-floating slab track in straight and curved segments is shown in Figures 9-11, and it can be seen that:(1) According to Figure 9, for the acceleration of the rail, the acceleration of the steel-spring-floating slab track is similar to that of the ordinary monolithic track, and is slightly larger than that of the ordinary monolithic track, which shows that the four working conditions are very close at the excitation level of the rail, so the vibration isolation and transmission of the track bed and the tunnel wall can be well compared. The rail accelerations under different line conditions are very close, and the rail acceleration in the curved segment is greater than that in the straight line segment, indicating that the excitation of the rail in the curved segment is slightly greater than that in the straight line segment.  
(2) According to Figure 10, for the acceleration of the track bed, it can be seen that the acceleration of the steel-spring-floating slab track is significantly larger than that of the ordinary monolithic track, and its amplitude is about 3-4 times that of the ordinary monolithic track. The reason is that the bottom of the ordinary monolithic track is fully constrained, while the bottom of steel-spring-floating slab track is only constrained by vibration isolators and the overall stiffness is small, so the dynamic effect is more significant under similar excitation conditions. The acceleration of the track bed in the curved segment also shows a similar law, and is slightly larger than the acceleration of the track bed in the straight line segment.  
(3) According to Figure 11, for the tunnel wall acceleration, the steel-spring-floating slab track segment is significantly smaller than the ordinary monolithic track segment, and the amplitude is about 0.2-0.3 of the ordinary monolithic track. It can be seen that when the excitations at the rail are similar, the steel-spring-floating slab track has an excellent vibration isolation effect, which can filter and weaken the vibration very efficiently, which is of great significance to ensure the vibration damping requirements along the subway line.