Failure mechanism and strengthening effect of shield tunnel lining reinforced by steel plates with corbels

This study investigates the failure mechanism and strengthening effect of a shield tunnel lining structure reinforced via steel plates with corbels. A detailed three-dimensional (3D) numerical model is established for the staggered-joint segmental lining structure of an actual shield tunnel in the Kunming metro-system, which is then validated via a full-scale simulation experiment of the shield tunnel segmental lining structure. Then, the actual loading conditions of the staggered-joint shield tunnel segmental lining structure in the Kunming metro-system are simulated, and the mechanical responses of the segmental lining are analysed in terms of the variation in its diameter, opening amount of the joints and stress of the bolts. The ultimate load-bearing capacity of the lining structure reinforced using steel plates with corbels is improved to 610 kN, which is 41.9% higher than the unreinforced structure with an ultimate load-bearing capacity of 430 kN. Moreover, the strengthening effect of the reinforcement using steel plates with corbels is discussed considering actual field monitoring data and other reinforcement methods. It is concluded that the results of this paper can provide an effective reference for similar reinforcement schemes of shield tunnels. The defined classification criteria can be adopted to determine the deformation stage of reinforced shield tunnels.