# Deformation Law and Control Limit of CRTSIII Slab Track under Subgrade Frost Heave
###### Abstract  
In order to find out the influence of subgrade frost heave on the deformation of track structure and track irregularity of high-speed railways, a nonlinear damage finite element model for China Railway Track System III (CRTSIII) slab track subgrade was established based on the constitutive theory of concrete plastic damage. The analysis of track structure deformation under different subgrade frost heave conditions was focused on, and amplitude the limit of subgrade frost heave was put forward according to the characteristics of interlayer seams. This work is expected to provide guidance for design and construction. Subgrade frost heave was found to cause cosine-type irregularities of rails and the interlayer seams in the track structure, and the displacement in lower foundation mapping to rail surfaces increased. When frost heave occured in the middle part of the track slab, it caused the greatest amount of track irregularity, resulting in a longer and higher seam. Along with the increase in frost heave amplitude, the length of the seam increased linearly whilst its height increased nonlinearly. When the frost heave amplitude reached 35 mm, cracks appeared along the transverse direction of the upper concrete surface on the base plate due to plastic damage; consequently, the base plate started to bend, which reduced interlayer seams. Based on the critical value of track structures' interlayer seams under different frost heave conditions, four control limits of subgrade frost heave at different levels of frost heave amplitude/wavelength were obtained. slab track; subgrade frost heave; track irregularity; interlayer seams; control limit +
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the slab track concrete had broken away in some sections, as shown in Figure 1, which could in turn seriously affect the slab track's service performance. It is therefore necessary to pave and maintain the slab track in severely cold regions in order to study the deformation and seams in the track structure of high-speed railways under subgrade frost heave and put forward control limits for subgrade frost heave displacements in frozen soil regions. Presently, most research on the subgrade frost heave displacement of high-speed railways has focused on the influential factors of frost heave formation and its developmental process [11; 12; 13]. A number of measures to reduce frost heave displacement, such as improving soil properties, temperature control and drainage, have been put forward [14; 15; 16; 17; 18]. Further, research on the influence of subgrade deformation on track structure has mainly analyzed subgrade settlement. For instance, [PERSON] [19] and [PERSON] [20] studied the deformation law of ballasted track under subgrade settlement using the finite element method. [PERSON] et al. predicted the long-term settlement of the track in transition zones and researched this dynamic behavior [21; 22]. Based on the discrete element method, [PERSON] et al. [23] discussed the influence of train load on track surface deformation during the settlement of ballasted track subgrade. [PERSON] et al. [24] investigated the relationship between different conditions of subgrade settlement and track irregularities by establishing double-block slab track on subgrade. [PERSON] et al. [25] explored the settlement limits of subgrade based on the bending moment of longitudinally connected slab track. [PERSON] et al. [26] used [PERSON]'s foundation composite beam theory and calculated the track surface geometric deformation law of unit plates and longitudinal connected slab track under different types of subgrade settlement. Based on the theory of vehicle-track coupling dynamics and using the finite element method, [PERSON] et al. [27] established an explicit dynamic analysis model for vehicle-slab track subgrade in the frost heaving area and researched the influence of frost heave amplitude and wavelength on the dynamic response of the vehicle track. [PERSON] et al.