Aerodynamic behavior of flaky spalled blocks in high-speed rail tunnel lining under slipstream

As high-speed railway tunnels continue to serve for long periods of time, the tunnel lining is subjected to long-term cyclic tension and compression from train aerodynamic loads, thereby causing cracks to propagate and spalled blocks to fall off, which severely impact the safety of train operation. This paper is based on the improved delayed detached eddy simulation (IDDES) method and establishes a 3D fluid–solid coupling calculation model of spalled block-high-speed train-tunnel-air. Explores the differences in the motion trajectory and force of spalled blocks falling off at different peeling times under the impact of a high-speed train traveling at 300 km/h, and investigates the relationship between the spalled blocks and the changes in train aerodynamic flow field structure and aerodynamic pressure during the motion process in order to understand the aerodynamic behavior and flow field structure mechanism of spalled blocks. Under the action of slipstream, the spalled blocks exhibit a combined form of translation and rotation while falling, with the translation mainly occurring in the longitudinal (X-axis) direction and the rotation being most obvious around the Z-axis. Some significant differences are observed in the translational trajectory and rotational angle of the spalled blocks in the vertical and horizontal directions at different peeling times, and the longitudinal displacement distance is 3 to 38 times the horizontal displacement distance. The maximum rotational angle of the spalled block that peels off when the train head arrives is along the Z-axis.