# Current Practices of Railway Ballastless Track Design Methods in China
## 1 Introduction  
As a fast and efficient mode of transportation, railways have developed rapidly in recent years. In China, as the high-speed railway network is gradually densified, the construction of urban express lines and urban rail transit systems between neighboring cities has also sped up. Various railway lines with different speed classifications cause more diversified demand for track structures. So far, a series of track structures of the Chinese railway track system (CRTS) are widely used in high-speed railways, intercity railways and many other railway lines in China. With the advancement of construction technology, the prefabricated track slabs, which are standardized and convenient for construction, have also gradually developed [1]. Under such a background, many new track structures have been generated and mainly used in some new urban express railway lines, which are relatively more lenient in criteria compared with the high-speed railway because of lower train speeds. The different track structures in China are shown in Figure 1, including CRTS tracks and some new prefabricated tracks. However, in different railway line classifications, the safety design values of size and reinforcement for track structures vary accordingly. Therefore, to accommodate the diversified development of railways in the future, the safety, flexibility and efficiency of the railway track design method is very essential. For track design under different conditions, appropriate design loads are vital for the adaptability of the structures. The size and reinforcement design according to expected loads should not only meet the requirements of safety, comfort and durability but also be more efficient. So, higher requirements are put forward for the design methods [2], and design loads should also be validly considered. So far, many scholars have studied the mechanical characteristics of a ballastless track under different loads [3], which provides important support for track design. Among the long-term loads on the track structure, the foremost one is the train load. Many scholars have conducted research on the dynamic and static mechanical properties of the track system under train loads [4; 5; 6; 7; 8]. [PERSON] [5] et al. constructed a full-scale model of a ballastless track on a subgrade and studied the dynamic response of the track and subgrade under different train speeds via experiments to obtain a rational dynamic load magnification factor. [PERSON] [6] and [PERSON] [7] analyzed the mechanical properties of railway tracks under train loads and revealed the influence law of wheel weights, speeds, load lengths and other parameters. [PERSON] [8] et al. proposed a new type of prefabricated slab track and verified its service performance under large freight train loads and fatigue train loads using numerical and experimental methods. In addition, the performance of the track structures is also affected by temperature changes [9; 10; 11; 12]. [PERSON] [12] et al. compared and analyzed the mechanical characteristics of unit slab tracks and piecewise slab tracks under a temperature gradient load, and the results showed that the coupling effect of the temperature gradient and train load would affect the vertical stability of track, and the stress and deformation of unit slab track were more significant. Furthermore, the influence of the deformation of the foundation on the track structure cannot be ignored either [13; 14; 15; 16]. [PERSON] [15] et al. analyzed the influence of uneven subgrade settlement (USS) on structural stress, deformation and damage of CRTS III slab tracks. The main parts and positions damaged and the most unfavorable wavelength range of USS are indicated. [PERSON] [16] et al. developed a segmental experimental model and studied the deformation characteristics of ballastless tracks under deformation of a long-span bridge by adding a test load. The research above on the mechanical characteristics of a ballastless track not only provided reference for the load values but also verified the design methods.