Risk Control Standard and Construction Control Technology of Shield Tunnel Passing through Irregular-Plate Bridge

As a kind of statically-indeterminate point-support structure, the irregular-plate bridge (IPB) is extremely sensitive to the settlement of pier columns, and the stress of the plate is complicated. Because of the limitation of environmental conditions, the newly-built subway circular symmetric shield tunnel needs to pass the pier foundation of the IPB perpendicularly. To control the engineering risks, the pier settlement value must be known, and measures should be taken to reduce the settlement. This paper takes the project of the Beijing subway circular symmetric shield tunnels passing the existing IPB of the Guang'anmen Bridge as an example. First, the stress characteristics and settlement control standards of the IPB are analyzed, and then the technical scheme of synchronous jacking and key points of risk control during the construction of the shield passing the IPB are put forward. The relationship between the excavation face pressure of the shield tunnel and pier foundation settlement, and the ground settlement, are then analyzed. Finally, structural cracking after construction is analyzed, and the analysis shows that synchronous jacking technology can effectively control the settlement value of the subway tunnel passing the IPB. The technology is a feasible method for controlling the safety of a tunnel passing through a sensitive, statically-indeterminate bridge, and this work is a successful experience for similar major risk projects.