Multifactorial damage of shear key groove in post-cast strip of China Railway Track System II slab track

Damage to the shear key grooves in post-cast strips at bridge ends of China Railway Track System (CRTS) II slab ballastless tracks is a critical issue threatening the safety of high-speed railways. This study investigates the damage mechanisms by integrating field measurements with finite-element simulations, analysing the stress state under the combined effects of train dynamic loads, temperature gradients and longitudinal forces from continuously welded rails. Results indicate that the instantaneous impact of train loads is limited, with peak stresses below 0.3 MPa for an eight-car consist and below 0.2 MPa for a 16-car consist. While this does not directly cause failure, it accelerates material fatigue. Crucially, under a negative temperature gradient, the maximum principal tensile stresses in the concrete at the top surface, side face and around the anchor plates approach 11 MPa, far exceeding the concrete’s ultimate tensile strength. Additionally, stress concentrations at the roots of the shear key grooves, induced by longitudinal forces, reach 2.65 MPa, surpassing the material’s bearing capacity. The research demonstrates that damage to the post-cast strips results from the superposition of multiple factors, with thermal effects being dominant. These findings provide a theoretical basis for optimising structural design and maintenance strategies for beam-end structures.