Structural Design and Construction Methods of Long-span Three-lane Quasi- ellipse Shield Tunnel without Columns

Abstract

Compared with the influence of open cut method during the construction of shallow-buried three-lane underground expressway on the surrounding pipelines, urban greening and traffic organization, as a fully-mechanized construction method, shield tunnelling has much smaller disturbance to the surrounding environment. A long-span three-lane quasi-ellipse shield tunnel was proposed and the inner contour was sketched according to the functional requirements of its internal space. To ensure the enough the bearing capacity and the anti-deform ability of the segmental lining, the structural design was finally determined after the sensitive analysis of certain key parameters. Then, a new type of segment lining with inner and outer surface pasted with thin steel plates was created, which made full use of the strong tensile strength of steel, and the mechanical behaviors of the lining were explored through the modified routine method. Given with the special shape, a corresponding segment casting method was chosen taking both of operability and structural integrity into account. To fulfil full face cutting, a quasi- ellipse shield machine equipped with a combined cutter head was designed, which could provide enough thrust force and minimize the disturbance to the surrounding environment in the working state.