Aerodynamic intensification effect and dynamic response of cracks on high-speed railway tunnel linings

Falling concrete blocks are serious problems in high-speed railway tunnels, and they cause delays of high-speed trains (HSTs) and even compromise driving safety. When HST-induced aerodynamic shockwaves propagate into cracks, the intensified pressure makes the cracks grow and connect, resulting in falling concrete blocks. In this study, the longitudinal, oblique and circumferential cracks at the tunnel vault are selected as representatives. The temporal, spatial and spectral characteristics of the aerodynamic pressure in the cracks are studied using the unsteady viscous k-ε turbulence model. The aerodynamic intensification effect in the lining crack is also revealed. Results show that the maximum pressure of the circumferential crack is 1.51 and 1.37 times that of the longitudinal and oblique cracks, respectively. On the basis of the results of soil–tunnel–crack models established in ABAQUS, two response surface models (RSMs) are established to quantify the effects of important factors, including crack length, crack depth, crack width, incident angle of the aerodynamic shockwave and train velocity, on the maximum tensile strain of the crack tip of circumferential cracks. Train velocity exerts the greatest influence on the maximum tensile strain in the circumferential crack, followed by crack width. Moreover, a field measurement is performed to investigate the dynamic strain of crack tips under train-induced aerodynamic loads and verify the proposed RSM. The maximum tensile strain caused by aerodynamic pressure is approximately 0.31–0.86 times of the maximum tensile strain of concrete. The proposed RSM can realise a reasonable prediction of the dynamic strain of crack tips. This research may be valuable for analysing the crack tip stability of tunnel lining cracks and guaranteeing the structural health of high-speed railway tunnels.