# Influence of Uneven Subgrade Frost Heave on Deformation and Damage of CRTSIII Slab Track
## 1 Introduction  
In recent years, with the rapid development of high-speed railway, CRTSIII slab track, as shown in Figure 1, which was independently developed by China, has been widely used due to its dual advantages: (a) stable performance and (b) convenient construction [1]. However, a detailed survey found that under uneven subgrade frost heave action, high track structure stiffness resulted in the track being incongruuous with foundation deformation [2]. This resulted in interlayer seam, finally leading to serious track irregularity and, in turn, threatening the safe operation of high-speed railway [3, 4]. Consider the example of the Harbin-Dalian railway, the world's first high-speed railway in Alpine areas. The total length of the railway is about 920 km, including 200 km in the seasonal frozen soil region. The annual average frost heave amplitude is about 5 mm, and the maximum frost heave amplitude is over 30 mm, which is far beyond the vertical displacement of the trackstructure limited by the design specifications of China's high-speed railway. Therefore, in order to ensure the safety of vehicle operations, the government has been compelled to reduce train speed [5]. In addition, when the displacement load generated by subgrade frost heave deformation is transferred to the track structure, each component is subjected to additional stress which is already high. This can easily damage the track structure concrete material [6], affecting the service state and service life of the track structure. In view of the frost heave problem in high-speed railway subgrade, many research studies have been carried out. Based on an independently developed set for a frost heaving monitoring system, [PERSON] et al. [7] carried out monitoring work of frost heaving on the Haqi railway subgrade and analyzed the cause of the frost heave. [PERSON] [8] analyzed the variations in characteristics of subgrade frost heave in a seasonal freezing region by monitoring frost heave deformation of the Harbin-Dalian railway subgrade. [PERSON] et al. [9] and [PERSON] et al. [10] analyzed variations in track irregularity before and after the freezing and thawing of subgrade. [PERSON] et al. [11] established a coupling analytical model of slab track and subgrade frost heaving of a high-speed railway. The study analyzed the influence of the subgrade's frost heaving wavelength and amplitude on the stress on various types of slab track structures. [PERSON] et al. [12] studied the influences of subgrade frost heaving parameters on the structural deformation and the interlayer seam of slab track. [PERSON] et al. [13] derived the 2D analytical equation of stress and deformation of frozen subgrade based on the thermo-elasticity theory, considering the effect of ice-water phase transformation. The researchers analyzed the influence of temperature load on the frost heave deformation of subgrade. On the basis of a single frost heave, [PERSON] [14] considered temperature and vehicle load for computations and analyzed the characteristics of track structure stress, interlayer seam, and rail irregularity under the combined action of complex loads. However, the influence of varying the longitudinal frost heaving position and the behavior of damaged track structure were not considered. The authors of [15; 16; 17] showcased the influence of the subgrade's uneven frost heave deformation on the vibration response of a high-speed railway track coupling system. The studies analyzed the influence of frost heave deformation on vehicles' operational safety. According to the static and dynamic indices of track structure and the dynamic response index of vehicles under frost heaving, a few scholars have proposed control limits of uneven frost heaving [18; 19; 20] and control measures for frost heave deformation [21; 22; 23]. However, in the studies carried out so far, track structures have often been regarded to be linear elastomers, which cannot simulate the damage and deterioration behavior of track structure under the condition of uneven subgrade frost heave.