Experimental study on evolution of mechanical properties of CRTS III ballastless slab track under fatigue load

Ballastless slab track have been developed and used worldwide to carter for high speed, high stability, high riding comfort, and low maintenance cost requirements of High Speed Railway (FISR) operations. To this ends, the Chinese Rail Track System (CRTS) Ill was designed and developed independently in China and adopted in new railway lines. The CRTS III is believed to have improved performance over the previously used CRTS I and II, severe structural damages in the form of cracks and delamination at the interface between the prefabricated slab and the SCC filling layer have been reported in service. This cannot be ignored because of the detrimental effects they have on bearing capacity and stiffness of the track. This paper presents an experimental study to evaluate the evolution of stiffness of fasteners and the isolation layer of CRTS Ill ballastless slab track. The experiments are based on full-scale test on three CRTS III slab track-subgrade structure model subjected to cyclic fatigue loadings up to 30 million cycles. The results of the study revealed the following: (1) The dynamic and static stiffness of the fastener increase by 116% and 30%, respectively. After 10 million cycles of fatigue loading, the ratio of dynamic to static stiffness become larger than 1.5. (2) the stiffness of isolation layer changes in accordance with quadratic function with a correlation coefficient of 0.999. The maximum stiffness obtains 2.4 times than its initial value at 30 million cycles of fatigue loading. (3) the acceleration of rail and slab track reduce by 63% and 34% respectively, while the acceleration of support foundation increases by 54%. The findings of this research can serve as a useful guide in the design and maintenance scheduling of the CRTS III slab track structure as well as references for future studies. (C) 2019 Elsevier Ltd. All rights reserved.