Abstract: To study the longitudinal equivalent bending stiffness of shield tunnel with doublelayered lining, the expression of longitudinal equivalent bending stiffness of shield tunnel with doublelayered lining is derived on the basis of simplifying the generalized longitudinal equivalent continuous model. A case study is conducted on Wusongkou Yangtze Rivercrossing tunnel in Shanghai, and the variation of longitudinal stiffness of doublelayered lining with the influence region of circumferential joints, the distance between deformation joints of secondary lining, and the thickness of secondary lining are analyzed. The results show the following. (1) The effective rate of longitudinal equivalent stiffness decreases with the increasing influence region of circumferential joints. When the influence coefficient of circumferential joints is less than 1, the effective rate of longitudinal equivalent stiffness decreases sharply with increasing influence coefficient of circumferential joints, whereas when the influence coefficient of circumferential joints is larger than 1, the effective rate of longitudinal equivalent stiffness decreases gently. (2) The longitudinal equivalent stiffness of tunnel increases with the increasing thickness of secondary lining and the span between deformation joints, and the increasing rate decreases gradually. Comprehensively, increasing the span between deformation joints is more beneficial than increasing the thickness of secondary lining.

Key words: shield tunnel, doublelayered lining, deformation joints, longitudinal equivalent continuous model, influence region of circumferential joints