## 4 Analysis of the Test Results
### Relative Displacement between the Track System Layers
#### 4.2.2 Longitudinal Relative Displacement between Layers  
According to the installation position of the LVDT displacement meter in Figure 5, when the upper structure layer slides horizontally to the left (to the fixed end side) with respect to the lower structure layer, the longitudinal relative displacement value is positive, and the reverse direction is negative.  
The horizontal and longitudinal relative displacements of the base plate and the beam body under the cyclic action of temperatures for a single day are shown in Figure 11. From the curve in the figure, it can be seen that the base plate at section 0 L slides to the right and left at \(\frac{1}{4}\) L. At 23:00, the displacement difference between the two positions is the largest at approximately 0.04 mm; the longitudinal relative displacement between the layers at section \(\frac{1}{2}\) L is close to zero, the base plate at \(\frac{3}{4}\) L slides to the right, and the displacement difference between the two positions is approximately 0.01 mm; the absolute value of the relative displacement of the base plate at L is the largest at 0.035 mm, and the relative displacement at section 0 L is 0.015 mm. Based on the analysis of the vertical relative displacement between the base plate and the beam, it can be concluded that the base plate moves upward relative to the beam in sections 0 L to \(\frac{1}{2}\) L, which are far away from each other, and moves downward in sections \(\frac{1}{2}\)-3/4 L, which are close to each other; the spatial relative displacement of the base plate at section L is greater than 0 L, which further verifies the restraint effect of the shear slots on the track system.  
Figure 12 shows the horizontal and longitudinal relative displacement curves of the track slab and base plate under the action of a 24-h daily temperature cycle. It can be seen from the figure that at 19:00, the longitudinal relative displacement of the track slab and the base plate is relatively large. Considering this curve analysis, it can be seen that the track slab at section 0 L has a right sliding trend with respect to the base plate, while horizontal longitudinal sliding does not occur at section \(\frac{1}{4}\) L, and the track slab at \(\frac{1}{2}\) L has a left sliding trend with respect to the base plate. According to the results of the vertical relative displacement between the base plate and the beam body, it can be inferred that the track slab in sections 0 L to \(\frac{1}{2}\) L moves downward relative to the base plate, among which the horizontal and longitudinal relative displacement between the track slab and the base plate at section \(\frac{1}{4}\) L is the smallest and the vertical relative displacement is the largest.  
The longitudinal relative displacement between the CA mortar layer and base plate is shown in Figure 13. In the process of a temperature cycle for a single day, the longitudinal displacement between the CA mortar layer and base plate is essentially negative, that is, the CA mortar layer has an overall right sliding trend relative to the base plate; the longitudinal relative displacement at section 0 L is the smallest (is essentially zero) in the whole test process; and the longitudinal relative displacement at section L has the largest change at approximately 0.03 mm.  
Figure 11: Displacement between the base plate and beam body.