Settlement Rule And Limit Analysis Of Irregularly Shaped Slab Bridge Caused By Tunnel Excavation

Tunnel excavation would produce differential settlement at the bearing of irregularly shaped slab bridge. Differential settlement of foundation would not only affect the normal use of the bridge, but also generate additional internal force on the bridge superstructure. Settlement became one of the important causes of bridge structure damage. For statically indeterminate structure, especially irregularly shaped bridge slab, the Specification does not define the permissible settlement value which should be determined by the stress state of structure, so the settlement problem needed further research for providing correct decisions and measures for tunnel excavation. Meanwhile, for ensuring the safety of the bridge in the subway construction and operation, it is necessary to predict the surface subsidence value caused by tunnel excavation and permissible settlement value of bridge structure itself Based on first-stage project of Beijing metro line 7 through the Guang-an-men overpass project, this thesis mainly carried on the following work:1) The mechanical properties of irregularly shaped slab structure was summarized. What’s mainly introduced was the type of irregularly shaped slab structure, internal force and stress condition, mechanical characteristics and its engineering application. Meanwhile, Finite element analysis Method of irregularly shaped slab bridge was summarized.2) The influence rule of foundation settlement of irregularly shaped slab structure was analyzed and discussed. Through ANSYS numerical simulation and theoretical calculation, the influence rule of irregularly shaped slab structure’s bearing force, internal force and displacement caused by foundation settlement was analyzed and obtained. In the same way, the influence factors that affected the permissible foundation settlement value of irregularly shaped slab structure was obtained.3) Combined with engineering project, Settlement Limit Analysis of irregularly shaped slab bridge near tunnel excavation engineering was conducted. The ground settlement value caused by tunnel excavation was predicted by comparing PECK formula theoretical calculation results and ANSYS finite element numerical simulation results. Based on the compression deformation characteristics of the rubber, the axial stiffness calculation formula of Circular plate rubber bearing was deduced, and the stiffness value of the bearing used in this engineering project was obtained. ANSYS finite element software was used to establish numerical analysis model of the partial prestressed concrete slab bridge. The foundation settlement caused structural response in aspect of the reaction force, displacement and stress was analyzed and discussed. Under the requirement of the secondary cracking level, the settlement standard of the bridge is obtained, and the corresponding engineering measures are put forward.