Experimental and numerical study on the mechanical behaviour of CRTS III slab tracks during the self-compacting concrete casting process

The casting of self-compacting concrete (SCC) is crucial for the safe operation of China Railway Track System type III (CRTS III) slab tracks. To elucidate the track structure’s mechanical behavior during construction, a full-scale experiment was conducted, and a coupled discrete element method (DEM) and multi-flexible body dynamics (MFBD) model was established. SCC flow, alongside track slab buoyancy, displacement, and deformation, was systematically analyzed. It was revealed that SCC flow involves four distinct stages. Track slab mechanical responses were observed to peak at the end of casting, resulting in an upward arching, with measured buoyancy of 42.99 kN and maximum vertical displacement of 0.88 mm. Furthermore, SCC fluidity is significantly influenced by aggregate morphology and gradation, which directly affects these mechanical indicators and casting time. To optimize construction quality and efficiency, reducing flaky aggregate content and balancing coarse aggregate proportions are recommended.