Mechanical properties of linings of shield tunnel strengthened by steel plates considering interface effects

To investigate the properties of the structure of segmental tunnel linings reinforced by steel plates, most of the existing studies assume that the interfaces between different materials are perfectly bonded, and thus ignore the discontinuous deformation characteristics of the steel-concrete interface, and then it is impossible to make a detailed analysis of the load-bearing behavior and failure mechanism of a structure. In this work, the cohesive-zone model is combined with the extended finite element method, and the discontinuous deformation characteristics of the connecting interface of the steel-plate-reinforced structure are considered. At the same time, a three-dimensional solid nonlinear model for the steel-plate-reinforced structure that can accurately describe the crack propagation process is established, and is validated through the tests. The dynamic simulation of the sliding failure and cracking of the interface between two different materials of steel and concrete is carried out, which makes up for the shortcomings of the tests. Thus, the mechanical properties of the reinforced structure under surface surcharge are analyzed. The results show that the stress failure process of the reinforced structure under surface surcharge can be divided into four stages. The cracking and bond failure of connecting interface between the steel plates and the concrete are the decisive factors for the failure of the reinforced structure. Under the action of the ground load, at the connecting interface joint of the reinforced structure, there are incompatible deformation areas with alternative tension and compression, which is more prone to shear slip and peel failure.