Experimental study on the dynamic characteristics of slab track structure considering local defects and temperature gradient

The unit slab track structure has been widely used in high-speed railways. Temperature gradients and local defects alter the interlayer condition of slab tracks, directly affecting the structure's dynamic performance. To investigate the impact of these critical factors, a full-scale experimental platform was constructed, incorporating standard and defective track sections with interlayer separations, along with a heating system and temperature/deformation monitoring system. This configuration achieved a positive temperature gradient of 90 °C/m within the slab. The influences of local interlayer defects, temperature gradients, and their coupled effects on track dynamics were studied by wheelset drop tests. The results indicated that the slab's vibration response significantly increased under local defects, particularly within the P2 resonance and slab bending resonance frequency bands. Under a positive temperature gradient, the temperature-induced deformation at defective slab corners increased, while upward deflection at slab centers decreased. For standard slab track, with the temperature gradient increased from 0 to 90 °C/m, the P2 resonance frequency gradually shifted downward from 80 Hz to 40 Hz, while vibration acceleration increased substantially. The coupling effect of positive temperature gradient and local defects enlarged the contact area between self-compacting concrete layer and baseplate. However, the structural stress at defects significantly increased under temperature gradient. • A full-scale platform was constructed to investigate slab track dynamics under temperature gradients and local defects. • A positive temperature gradient of 90 °C/m within the slab track was achieved in laboratory. • The dynamic response characteristics of slab track with local defects were evaluated by wheelset drop tests. • The structural dynamic properties and the coupling mechanism between local defects and temperature gradients were studied.