Study on the Impact of Track Types on Tunnel and Environment Vibration

Based on the subway tunnel in Ningbo, the differences in dynamic responses in the tunnel and surrounding soil between the monolithic track and the steel spring floating slab track were studied through combining field measurements and 2.5-dimensional Finite Element Method (2.5 D FEM). It is found that the steel spring floating slab track can absorb more high-frequency vibration above 10 Hz than the monolithic track. When the tunnel burial depth is less than 20 m, with the higher the train speed and the shallower the tunnel burial depth, the vibration reduction effect of the steel spring floating slab track is stronger. However, the single-phase elastic medium that is used to simulate the surrounding soil will underestimate the intensity of vibration in the tunnel and overestimate the vibration reduction effect of the steel spring floating slab track. The excess pore pressure response around the tunnel is related to the train speed and track type, but independent of the tunnel burial depth. The research results show that the application of a steel spring floating slab track not only reduces the environmental vibration but also effectively reduces the excess pore pressure in the soil around the tunnel, which is beneficial to controlling the tunnel settlement.