Numerical simulation of the time-history of longitudinal displacement of railway shield tunnel in soft soil area during operation period

In this study, the finite element simulation method was used to establish the finite element model of the soft soil base-shield tunnel-track structure, and the time history of the longitudinal displacement of the shield tunnel section under the train load in a coastal area in operation was analyzed and studied. Based on the mechanical background of creep in soft soil, the evolution and recovery of tunnel longitudinal displacement during operation period and night maintenance period, the change of tunnel longitudinal displacement during one year of railway operation, and the influence of railway acceleration on tunnel longitudinal displacement were studied. The conclusions are as follows :(1) the recovery of tunnel geometry during night maintenance time is small and negligible;(2) after the tunnel was put into operation, it showed a slight upward floating trend, and the upward floating in about 100 days had reached more than 90% of the one-year upward floating volume;(3) if the railway is accelerated to 200km/h for operation, the impact on the tunnel geometry is relatively small. At the same time, based on the above data, this paper puts forward a suggestion on the operation safety of the tunnel section near the station.