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Rock and Soil Mechanics

Abstract

When shield is driving along a curve alignment or during deviation correction, the asymmetrical thrust will generate an additional bending moment at the head of the tunnel, which will cause construction problems such as longitudinal deformation of the tunnel and dislocation between rings. Based on the theory of elastic foundation beam, the shield tunnel is simplified as a Timoshenko beam in Winkler foundation, an analytical model for evaluating the additional response of the shield tunnel induced the asymmetric thrust is established, and the analytical solutions of longitudinal deformation and internal force of shield tunnel are deduced. Then the correctness and applicability of the analytical solutions are verified based on the finite element method, and the sensitivity of key parameters in the analytical model is further analyzed. Finally, the influence range of additional bending moment and the second order effect of shield thrust are discussed. The research results show that the proposed analytical model is reliable and has good applicability for evaluating the additional response of shield tunnel under asymmetric thrust. The influences of foundation stiffness and tunnel stiffness on the longitudinal deformation of the tunnel are more significant than the internal force. The influence range of the additional bending moment is more sensitive to the changes of the foundation stiffness, and an exponential attenuation relationship is found to exist between the two. The shield thrust improves the longitudinal bending stiffness of the tunnel, and the second-order effect produced is relatively low. Under the condition of lower bending stiffness of tunnel and foundation stiffness, the second-order effect of axial force is enhanced.

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