Failure mode of interlayer connection of longitudinally-connected ballastless track-bridge system under uneven pier settlement

Abstract

• Proposing the characterization model of uneven pier settlement and interlayer connection failure in LBTBS. • Analysing the generation mechanism and development law of interlayer connection failure caused by uneven pier settlement. • Describing the evolution law of interlayer contact behavior of each layer of track caused by uneven pier settlement considering the existing interlayer connection failure. The generation and mechanical balance mechanisms and the deformation compatibility relationship of interlayer connection failure (ICF) of a longitudinally-connected ballastless track-bridge system (LBTBS) caused by uneven pier settlement is analyzed in this paper. The characterization model of the uneven pier settlement and the ICF of the LBTBS was derived based on Castigliano's Second Theorem, Linear Superposition principle, Heaviside function, and Tension-free Winkler beam. The characterization model was further verified by the field measured data and finite element model results. Finally, the development law of the ICF of the LBTBS caused by uneven pier settlement based on the characterization model was analyzed. The results show that the calculated results of the characterization model agree well with the field measured data and finite element model results, which verifies the correctness of the characterization model. Under uneven pier settlement, a void beneath the slab first appeared between the base slab and bridge, and then mortar debonding occurred between the CA mortar and track/base slab when settlement value is 193.48 mm. The maximum height of void beneath the slab developed away from the beam gap, and when the settlement value was less than 8.434 mm, the void beneath the slab length in the left area of the settlement pier was greater than that of the adjacent pier. With the increase in mileage, the height of the void beneath the slab and mortar debonding increased first and then decreased. In practical engineering, mortar debonding is not easy to notice, and the void beneath the slab between the base slab and the bridge should be inspected regularly. The existing fastener failure had little influence on developing a void beneath the slab caused by the uneven pier settlement. The existing mortar void aggravated the occurrence of mortar debonding. When the existing mortar void length exceeded 5 m, the mortar debonding length at both ends of the adjacent pier was about 1/2 of the existing mortar void length. When the length of the existing mortar void was less than 1 m, there was little effect on the length of the void beneath the slab.