DISTRIBUTION AND EVOLUTION CHARACTERISTICS OF CIRCULAR TUNNEL LINING DAMAGE DUE TO LONG-TERM TRAIN LOADS

To investigate the damage distribution and evolution of the tunnel lining by train loads, the incremental damage constitutive relation under complex stress state was derived based on the uniaxial tension and compression constitutive relation in the Code for design of concrete structures and embedded into the standard calculation program of ANSYS. Its reliability was verified through a comparison with the uniaxial tension and compression experiment results. The coupled circular tunnel-soil dynamic FE model was then established. Based on the improved Miner’s cumulative damage theory, the damage distribution, dynamic response and the evolution of damage increment and cumulative damage of tunnel lining due to long-term train loads were studied. It is found that the long-term train-induced damage is symmetrical about the tunnel centerline, and mainly distributes in the inverted arch with an angle of 120 degree. There are two damage concentration areas right beneath the train load applying points, where the damage amplitude is larger than any other areas. With the increase in train operation time, the amplitude of single train-induced dynamic stress in concentration area decreases by about 83% whereas that of dynamic strain increases by about 150%. The damage increment and cumulative damage both increase nonlinearly with the increase in train operation time. Accordingly, the improved Miner’s cumulative damage theory could improve the accuracy for fatigue life prediction of tunnel lining.