# Deformation Law and Control Limit of CRTSIII Slab Track under Subgrade Frost Heave
## 4 Laws of Track Interlayer Seams under Subgrade Frost Heave
### Seams between the Self-Compacting Concrete and Base Plate  
When studying the law of the seams between the self-compacting concrete and base plate, considering that a frost heave wavelength of 10 m is relatively common in severely cold areas and has a great influence on the mechanical characteristics of the slab track [39; 54], the frost heave wavelength is set at 10 m. As shown in Figure 12a, when the frost heave amplitude is small due to the track slab's warping deformation, the seams between the self-compacting concrete and base plate only occur at the end of the track slab; yet when the frost heave amplitude increases, the warping deformation becomes obvious. When the frost heave amplitude is 40 mm, the seam range and height greatly increase. In order to study the seam development process, the distribution cloud with a seam height greater than 1.0 mm under different frost heave amplitudes is extracted, as shown in Figure 12b. When the frost heave amplitude is small, the seam only exists at the end of the slab. When the frost heave amplitude increases, the seam range also increases, which is consistent with the results shown in Figure 12a. When the frost heave amplitude is 12.42 mm, the seam range extends from one slab to two slabs. When the frost heave amplitude reaches 18.92 mm, these seams appear below the three slabs, and the range reaches about 1.5 slabs. When the frost heave amplitude reaches 27.60 mm, the lower section of a slab is almost completely void. When the frost heave amplitude is 40 mm, the seam range can reach a length of 2.5 slabs.  
From Figure 13a, when the frost heave wavelength is 10 m, the seam height and length increase linearly with increases in frost heave amplitude. When frost heave amplitude increases from 5 mm to 40 mm, the seam height and length increase by 7.64 times and 22.10 times, respectively. This means that the effects of frost heave are rather obvious. As shown in Figure 13b, when the frost heave amplitude is 10 mm, the frost heave wavelength increases from 5 m to 10 m. The seam height is reduced to 3.18 mm from 5.53 mm, and the seam length decreases from 6.77 m to 1.42 m, resulting in reduction ratios of 43.4% and 79.0%, respectively. When the frost heave wavelength increases from 35 m to 40 m, the seam height is reduced from 0.77 mm to 0.69 mm, and the seam length remains unchanged. That is, as the frost heave wavelength gradually increases, both the height and length of the seam decreases, and the reduction range is gradually reduced. In addition, when the frost heave wavelength reaches 28 m, the maximum height of the seam is 1.0 mm; that is, the seam height gradually decreases in response to the increase in wavelength. There is an indication that when the frost heave wavelength exceeds 28 m, no seam changes occur.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Frost Heave Position** & **A** & **B** & **C** & **D** & **E** \\ \hline Seams between the self-compacting concrete and base plate & Height & 0.38 mm & 1.07 mm & 3.18 mm & 3.91 mm & 0.79 mm \\ \hline Seams between the base plate and subgrade & Length & 0 m & 0.18 m & 1.42 m & 1.15 m & 0 m \\ \hline \hline \end{tabular}
\end{table}
Table 3: The height and length of seams under different frost heave positions.  
Figure 12: Seams between the self-compacting concrete and base plate under different amplitudes of frost heave displacements. (**a**) Deformation law of track structure; (**b**) development law of seams.