# Influence of Uneven Subgrade Frost Heave on Deformation and Damage of CRTSIII Slab Track
## 4 Results and Discussion
### Influence of Frost Heaving Positions on Subgrade  
Based on the symmetry of the CRTSIII slab track itself, seven frost heaving positions, i.e., from (a) to (g), were selected in the 2\(\#\) concrete base area, as shown in Figure 12. By considering the classical cosine function of the 20 mm/10 m (wave amplitude/wavelength) subgrade frost heaving curve as an example, an analysis was performed to understand the influence of deformation and damage of slab track when the frost heaving wave peak acted at different positions. Figure 13a,b respectively, show the self-compacting base interlayer seam and the base subgrade surface interlayer seam under the action of various frost heaving positions. Table 2 shows the peak value and position of the self-compacting base interlayer seam. It can be observed that the peak value of the self-compacting base seam predominantly occurs at the position of self-compacting concrete edge. When the frost heaving wave peak appeared at (e), due to the lack of longitudinal constraints at the right end of the base and the formation of a lever system in the middle of the self-compaction concrete, the seam in between the layers reached the maximum value at 7.94 mm. When the frost heaving wave peak appeared at (g), the deformation of the track structure at both ends was relatively well coordinated, as the lever fulcrum did not form at the expansion joint position. Hence, the seam within layers was the least, with a value of 1.01 mm. The interlayer seam between the base and subgrade surface appeared on both sides of the frost heaving wave peak. When the frost heaving wave peak position varied from (a) to (g), the peak values of the interlayer seam were 6.59, 4.78, 3.43, 3.99, 8.50, 4.00, and 2.71 mm, respectively, which  
Figure 11: Longitudinal stress of the track structure: (**a**) Longitudinal stress of the composite slab; (**b**) longitudinal stress of the concrete base. Figure 12: Schematic diagram of the frost heaving positions. were all higher than those of the interlayer seam between the self-compacting concrete and base. This is because the stiffness difference between the base and subgrade surface was greater than that between the self-compacting concrete and the base, which would cause greater deformation disharmony in the former. The maximum and minimum interlayer seam also occurred when the frost heaving wave peak positions were (e) and (g). Therefore, it is necessary to give more attention to the interlayer seam of the track structure when frost heaving wave peak acts on (e). Based on the above determination of the distribution characteristics of interlayer seams, the following preventive measures can be taken. Vertical reinforcing bars connected to the base can be arranged at both ends of the self-compacting concrete, which can effectively inhibit the seam between the self-compacting concrete and the base. To increase the biting force between the base and the subgrade surface, an anchor treatment can effectively inhibit the formation of an interlayer seam between the base and the subgrade surface. Figure 14 shows the subgrade frost heaving values when the frost heaving wave peaks vary from (a) to (g) and damage along with macroscopic cracks appear on the base. It can be observed that when the frost heaving wave peak was close to the base center and its groove, i.e., when it acted on (b), damage and macroscopic cracks appeared on the base initially. When the frost heaving wavelength was 10 m and the frost heaving value reached 2.43 mm, damage started to appear. Macroscopic cracks appeared on the base when the  
Figure 13: Interlayer seam: (a) Self-compacting base interlayer seam; (b) base subgrade surface interlayer seam. first heaving value reached 3.83 mm. It was also observed that, wave peaks at (a), (c), and (d) also easily lead to damage on the base. Figure 15 shows the tensile damage to the slab and the base when the frost heaving peak acts at different positions. The damage of the base mostly occurs at the position of the base groove.