Model tests on effect of bonded steel plate reinforcement of shield tunnels under different deformation conditions

Due to the impact of surrounding projects such as stacking and excavation, it has become a common problem for metro tunnels to produce large deformations. At present, the means to control tunnel deformation is mainly the bonded steel plate reinforcement method, but the existing researches on the evaluation and analysis of the effect of bonded steel plate reinforcement are not clear. Based on the indoor model tests with the similarity ratio of 1:5, the bearing capacity, load-displacement relationship and structural failure mode of shield tunnels reinforced by the bonded steel plates under different deformation conditions are studied. Furthermore, the effects of bonded steel reinforcement and reasonable reinforcement timing are analyzed. The results show that: (1) When the vertical deformation are 7.4‰D, 15‰D and 20‰D respectively (D is the outer diameter of the tunnel), the bonded steel plate reinforcement is adopted for the tunnel structure. Compared with the original structure, the failure loads of the structure reinforced by the bonded steel plates increase by 54.2%, 49.6% and 26.7% respectively, the vertical deformation at structural instability is 60.78, 58.74 and 62.15 mm respectively, and the horizontal deformation at structural instability is 48.46, 56.28 and 61.68 mm respectively, indicating that the bonded steel plate reinforcement can improve the structural bearing capacity, and it has no great influence on the unstable displacement, thus providing a basis for judging the structural service performance based on the displacement change. (2) It is more reasonable to use as the reinforcement time when the structural deformation is between 10‰D and 15‰D. (3) The cracking and peeling of bonding surface between steel plate and concrete are the main factors for the failure of bonded steel reinforcement structures, and the critical position is the joint near vault. These findings can provide a theoretical basis for the reinforcement design and selection of reinforcement time.