Simulation Study On The Mechanical Behavior Of Effect Of Shield Construction On Existing Bridge And Tunnel

The down-traversing design and construction of the subway in complex conditions is faced with the new challenge that there is less cases of undercrossing shield tunneling construction on the existing urban tunnel and viaduct pile at present. Therefore, there is a positive significance to research on the influence to surrounding buildings of undercrossing shield tunneling construction on the existing viaduct and urban tunnel. Based on the project of Hefei Metro Line 1, the huge hidden danger of crossing viaduct piles from the side and undercrossing existing urban is researched by this paper. Combined with numerical method and field monitoring method, the change law of the pile force, horizontal deformation and ground settlement were analyzed under different working conditions during the process of shield advancing. And the pile entity structure element was discussed about the feasibility of calculation method of bending moment and shear force. The research shows that:(1) In the process of excavation, shield tunneling has great effect on the deformation and stress of tunnel structure. Besides, the deformation and stress of the existing buildings and structures have additive effect under the influence of the shield with two lines of excavation.(2) Based on the fitting displacement of discrete monitoring points, the calculated method of bending moment and shear in the condition that shield tunnel is adjacent to existing viaduct pile foundation is feasible.(3) The effect of shield construction with the close space on theviaduct pile is little. It is because that steel sleeve set outside bridge pier in advance has ideal protection with bridge pier.(4) The trend of viaduct pile bending moment and shear force is closely related to the position of shield construction:as the shield gradually close to the pile, bending moment and shear force of the pile increases continuously, and excavation of double shield tunnel in turn has impact on the internal force of viaduct pile with superposition effect(5) The existence of the pile foundation and cap can control the surface settlement to a certain extent.(6) Based on the calculation and monitoring results, some proposals and measures were put forward to the practical engineering construction.