Vibration Response and Cumulative Fatigue Damage Analysis of Overlapped Subway Shield Tunnels

Abstract

Overlapped subway shield tunnels are subjected to the dynamic impacts caused by running trains and are damaged during their long-term service life. In this paper, the dynamic response and cumulative damage evolution of the overlapped shield tunnels were numerically studied. The numerical simulation takes into account the uniaxial constitutive concrete model and the fatigue damage constitutive model of steel-reinforced concrete that is able to simulate any number of loading (cycling) times. For simplicity, only the case of a train running in the upper tunnel is considered in this study. The fatigue life of the overlapped tunnel section is numerically computed. The results indicate that the fatigue life meets the design requirements. The maximum principal stress is mainly concentrated at the bottom arch in the upper tunnel as the train runs in the upper tunnel. The lower tunnel is subjected to smaller damage than the upper tunnel. The tunnel structure undergoes greater tensile damage than the compressive damage in terms of damage amplitude and range. The failure of the structure is mainly associated with tensile damage. The cumulative damage of overlapped shield tunnels indicates a two-stage feature: the rapid increase stage (0–6.85 years) and the slow development stage (6.85–102.74 years). The steel spring floating slab can greatly reduce the cumulative compressive and tensile damage of the bottom arch at the upper tunnel.