Study On The Deformation Mechanism Of Metro Shield Tunnel Lining Strengthened By Steel Plates With Steel Corbel

The strengthening technology through steel plates with steel corbel is applied for metro shield tunnel with an excessive deformation in the diameter direction caused by external construction,after which the ballast should be reconstructed.To investigate the deformation mechanism of lining structure before and after steel plate reinforcement,the numerical simulation method is implemented and verified by test of single lining ring reinforced by steel plates with steel corbel in Shanghai.Based on the verification,the similar simulation process is applied for actual reinforcement case in Kunming metro shield tunnel assembled in the staggered pattern.Subsequently,the deformation mechanisim of lining structure before and after reinforcement is analyzed through the diameter deformation,the splaying amount of joints and the bolt stress.Besides,the strengthening effect of different reinforcement forms and the optimization of reinforcement parameters are discussed.The main contents are summerized as follows:(1)Bassed on a full-scale structural test of single lining ring reinforced by steel plates with steel corbel in Shanghai,a detailed single-ring model is established.The model carefully describes the details of hand hole,bolt,watertight gasket,bonding surface and steel plates with steel corbel,etc.The simulation results are promising compared with test results and it is believed that the simulation process is reliable for understanding deformation mechanism.(2)Depending on the actual reinforcement case in Kunming metro shield tunnel assembled in the staggered pattern,a 3D "one full ring + two half rings" detailed model is establishedfor investigating the deformation mechanism.Compared with the deformation mechanism of lining structure without reinforcement,it is considered that shield tunnel lining should be strengthened when the ellipticity value of lining ring achieved 25‰D.While grounded on the analysis of reinforcement model,it is shown that the ultimate capacity of the shield tunnel is remarkably improved by 41.9% after reinforcement.Moreover,the bond failure between the steel plates with steel corbel and the lining ring leads to the failure of the strengthened structure.(3)Different reinforcement forms of shield tunnel are conducted for comparison of strengthening effect,that is,the comparison between shield tunnel assembled by staggered joints or straight joints,the comparison between reinforcement by full-ring steel plate or steel plates with steel corbel and the comparison between reinforcement by steel plate with steel corbel and just joint reinforcement.The results can provide references for chosing the corresponding reinforcement forms of shield tunnels.(4)Different reinforcement size of the steel plates with steel corbel are selected to discuss the influence on the ultimate capacity of the shield tunnel in the staggered pattern.The size of the steel plates,the size of the steel corbel,the reinforcement time,and the ultimate tensile strength of the bonding surface are included and analyzed.The results can provide references for the optimization design of the steel plates with steel corbel.