Abstract: To investigate the impact of shield tunnel on pileraft foundation of existing railway station and the constuction control technology, a case study is conducted on a shield tunnel of Hangzhou metro line 5 crossing underneath Hangzhou south railway station. Then, the interaction between the shield tunnel and the pileraft foundation of the existing railway station is analyzed through numerical simulation and measured data. Moreover, the deformation of surface and the existing station and the deformation of the pile foundation are examined, and the numerical simulation results are validated by measured data. Finally, corresponding construction control technologies are proposed. The results reveal the following: (1) The pile raft foundation at the center line of the twintunnel can effectively reduce the soil settlement under the station floor and the secondary disturbance caused by construction. (2) During shield tunnel underpassing, the peak values of displacement, bending moment, and shear force of adjacent pile foundation appear at the bottom plane of the tunnel, which can provide reference for reinforcement and support scheme. (3) When the tunnel passes through muddy clay layer, the conservative design can be carried out according to the formation loss rate of 2%. In the actual construction, the formation loss rate can be reduced by secondary tracking grouting. (4) By adjusting the shield posture and injecting quick setting slurry above the shield, the upward floating of the shield tunnel can be effectively controlled.

Key words: shield tunnel, pileraft foundation, ground loss rate, tunnel uplift, control measures