Research On Interlayer Connection Status And Improvement Measure For CRTSâ…¢ Slab Track

As the new track structure with completely independent intellectual property rights in China, CRTSâ…¢ slab track has been successfully used on the passenger dedicated lines including Chengdu-Dujiangyan railway line, Wuhan intercity railway line, Shenyang-Dandong railway line, and Panjin-Yinkou railway line. The interface between the track slab and the self-compacting concrete layer is vulnerable for the CRTSâ…¢ slab ballastless track. This paper mainly focuses on the interface between the track slab and the self-compacting concrete layer of the CRTSâ…¢ slab track. The main research contents and conclusions are listed as follows.1. Based on the field investigation, the diseases of the interface for the ballastless track were summarized. Based on the theory of the new-to-old concrete interlayer weakness, it was elaborated that the self-compacting concrete, construction process, environment, and train load were the main reasons to cause the interlayer diseases for the CRTS â…¢ slab track. It provided a reference to the design and construction of CRTS â…¢ slab track.2. The static model of the CRTS â…¢ slab track on bridge was built, the interlayer stress with consideration of the action of the percentage of contraction of the self-compacting concrete and the temperature gradient was analyzed. And based on the empirical formula for the interlaminar shear stress peak, the shear failure was analyzed.The results show that under the effect of contraction alone or under the combined effect of contraction and negative temperature gradient, the shearing damage occurred at 6-7cm from the slab edge as the percentage of contraction is greater than or equal to 3.5/104. The shearing damage occurred at the convex block as the percentage of contraction is greater than or equal to 4/104. Under the combined effect of contraction and postive temperature gradient, the shearing damage occurred at 6-7cm from the slab edge as the percentage of contraction is greater than or equal to 3/104. The shearing damage occurred at the convex block as the percentage of contraction is greater than or equal to 3.5/104.3. Due to the vulnerable condition for the interface between the track slab and the self-compacting concrete layer for the CRTS â…¢ slab track, a new type of CRTS â…¢ slab track has been designed, in which the truss-type reinforcement is replaced by the door-type reinforcement. Then the reinforcement design and check calculations have been conducted for the track slab, the self-compacting concrete layer and the baseplate.4. By means of the finite element software, with consideration of the contact loss between the track slab and the self-compacting concrete layer, the interface between the track slab and the self-compacting concrete layer was simulated by the contact element. Under the effect of the positive and negative temperature gradient, the mechanical properties of the old and new type CRTS â…¢ slab track were compared and analyzed. The reasonablility of the new type CRTS â…¢ slab track was verified.The results show that under the effect of temperature gradient, the stresses of new type CRTS â…¢ slab track were smaller than those of the CRTS â…¢ slab track except for the longitudinal tensile stress of the self-compacting concrete. The largest tensile stress for the truss-type reinforcement and the door-type reinforcement occurred at the interface betwee the track slab and the self-compacting concrete layer. The tension-compression stress for the truss-type reinforcement was smaller than that for the door-type reinforcement. The largest concrete tensile stress around the truss-type reinforcement was smaller than that for the door-type reinforcement.