Abstract: This paper presents a case history of safety hazards evaluation of the shielded tunnel excavation under pass the existing highway bridge in the Suzhou Rail Transit No. 6 Line under passing the Changtai Expressway at location between Xujiabang and West Zhongxin Avenue stations. The influence of the relative location between the shielded tunnel and the expressway bridge on the safety hazards was evaluated by the three-dimensional finite element method and the stress and deformation of bridge piers induced by the tunnel excavation were simulated. The numerical simulation results indicate that, the deformation of the bridge piers is mainly in the traffic (longitudinal) direction with a maximum deflection of 3.3 mm. The maximum differential settlement is 0.39 mm. If the shielded tunnel excavations could use the zoned method and the control of amount of grouting, the bridge pier deformation could be controlled within the tolerable range. 

Key words: shielded tunnel excavation, expressway, bridge viaduct, numerical simulation, safety hazards