Deformation Effect Analysis of Shield Tunnel Closely Side-passing Viaduct Pile Foundation

Objective Shield tunneling may cause displacement and deformation of the nearby viaduct foundation and reduce its bearing capacity. Therefore, the deformation effect caused by shield tunnel closely side-passing viaduct foundation is studied based on an actual project. Method Relying on the project of Hefei Metro Line 5 in which the shield tunnel passes the pile foundation of the viaduct on the side, a three-dimensional numerical model is established to analyze the horizontal displacement,the longitudinal displacement and the settlement pattern of the pile foundation caused by shield construction. Result & Conclusion The research results show that the horizontal displacement at the pile bottom presents dynamic changes of leaving, approaching and leaving the tunnel. The horizontal displacement of the pile body is similar to a C shape flexture curve. The displacement increases first and then decreases along with the pile depths, and the extreme value is located at the pile depth of 9~10 m. The longitudinal displacement at the pile bottom （parallel to the tunnel axis） shows a bimodal curve. After the shield passing the pile foundation, the pile body undergoes longitudinal deformation in the opposite direction of the excavation. After the shield passing through the pile foundation for 12m and further, the horizontal displacement of the pile body in longitudinal direction rebounds, indicating that the influence of shield tunneling on the longitudinal deformation of the pile foundation is reversible to a certain extent. The settlement of the pile foundation presents a steep trend. The closer the pile foundation at the same side is to the tunnel, the greater the settlement. Moreover, the excavation of the far side tunnel will cause secondary settlement of the pile top. The maximum settlement occurs at the bottom of the No.4 pile foundation, and the settlement value is 4.94 mm.