Computational Model of Outer Circle and Inner Ellipse Shield Tunnel Lining Structure

Subway tunnels are mostly located in strata with an uneven pressure. This uneven pressure is usually manifested by lateral pressure coefficients less than 1. To adapt to the unevenness of the stratum load, in this study, we propose a new shield tunnel lining structure—outer circle and inner ellipse shield tunnel lining structure—whose outer contour remains circular and the inner contour shape of the structure is designed according to the load conditions. We used the stiffness step discounting method to obtain the calculation coefficients used in the force method formulas and established the calculation model of the outer circle and inner ellipse shield tunnel linings. The force method was then used to determine the force distribution characteristics of the outer circle and inner ellipse shield tunnel lining structure. During the verification, it was sufficient to analyze whether the waist structure rigidity met the safety conditions. This simplifies the design elements. The internal space area of our proposed design is expanded by 0.86 m² compared to the internal space area of the equal stiffness shield tunnel lining design.

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