As one of the core technologies of HSR, the ballastless track system once monopolized by Japan and Germany for a long time is designed with the layered concrete structure in replace of the traditional granular ballast bed, featuring high regularity, high stability and less maintenance. In order to meet the initial construction requirements of HSR, China established the CRTS I and CRTS II slab ballastless track systems on the basis of the introduced technologies. Due to the differences in climate and geological conditions and technical limitations, problems occurred one after another, such as high-temperature camber and low-temperature fracture, gap failure and life cycle mismatch of structural layer, and unstable track circuit information transmission, resulting in a significant impact on the track service quality, maintenance cost far higher than expected, and operation speed reduction in some sections. In order to comprehensively solve the above problems and break the foreign technical barriers, with the support of the state and relevant ministries and commissions and technical research over a decade, a complete technology of CRTS III ballastless track system for HSR with independent intellectual property rights has been formed through collaborative innovation among the industry, universities, researchers and enterprises, overcoming the three major technical difficulties of coordinated action, stable and reliable performance, high-precision and efficient construction of multi-layer structural system under complex environmental conditions. Consequently, China became the original country of ballastless track system for HSR, laying a solid foundation for "go global" of HSR. Key innovations of the project are as follows:
1. A new design method of the ballastless track structure system for 350 km/h HSR was created. The full-scale model test, the long-term monitoring tests of dynamic performance and operation state of real train under different environmental conditions were carried out, and massive data statistical analysis was completed, and the static and dynamic refined analysis model of ballastless track was built under the multiple-field coupling action, such as train high-frequency dynamic load, temperature load and foundation deformation. The deformation coordination mechanism and vibration transmission law of such a multi-layer structure was revealed, and the design method and parameter system for the global environment of ballastless track were put forward, and the problems of coordinated action of the multi-layer structure system under the joint effect of complex environment conditions and high speed train were solved.
2. A new ballastless track structure system for 350 km/h HSR was developed. The composite structure system of "vertical double-layer composite and longitudinal stress relief" ballastless track was originated, realizing stress relief, track geometry maintenance and the same life among structural layers. The fastening technology of ballastless track with high elasticity, high fundamental frequency and high fatigue strength was innovated, and the difficulties of fitting of rail fastening and base plate under large deformation conditions, and high frequency resonance were solved. The multiple insulation technology of ballastless track system under transient alternating strong magnetic field and track circuit continuous magnetic field environment was innovated. The technical problem of stable and reliable structural system under the joint effect of complex environment and high speed train was solved.
3. The new technology of high-precision and efficient construction of the ballastless track structure system for 350 km/h HSR was innovated. The high-precision and efficient intelligent manufacturing technology of bi-directional pre-tensioned prestressed track slab based on the assembly line method was initiated. The complete laying equipment based on inertial navigation and track precise survey network was developed. A digital construction technology of ballastless track structure system based on the design spatial alignment and taking the high track regularity as the core was formed. The millimeter-level efficient construction technical difficulties of ballastless track were solved.
The research outcomes comprise 19 standards formulated and participation in the preparation of the ballastless track system standards of International Organization for Standardization's (ISO) as the presiding entity; 32 invention patents and 66 utility models granted, including 8 international patents; 3 software copyrights granted; 4 monographs and more than 170 papers published; 1 provincial and ministerial special prize, 3 first prizes and 3 Chinese Patent Awards of Excellence rewarded. The research results have been popularized and applied on dozens of HSR lines such as Beijing-Shenyang HSR, Beijing-Xiongan Intercity Railway and Shangqiu-Hefei-Hangzhou HSR, with more than 12,000 km in length, providing solid support for the successful implementation of 420 km/h crossing and coupling comprehensive test on Zhengzhou-Xuzhou HSR, and has been applied in the HSR projects oversea such as Jakarta-Bandung HSR in Indonesia, as the only HSR ballastless track system reaching the international leading level and "going global" so far.