Numerical Study On Bearing Behavior Of Metro Shield Tunnel Reinforced By AFRP

AFRP(aramid fiber reinforced polymer) reinforcement and steel plate reinforcement are common methods of repairing metro shield tunnel. The former is widely applied due to its convenient construction, low cost, good reinforcement effect. According to the different diseases of tunnel, AFRP reinforcement is embodied in three aspects:(1) when lateral deformation of tunnel is small, AFRP is used to reinforce the whole-ring shield tunnel,(2) when the opening of top longitudinal joint of tunnel is excessive, AFRP is used to reinforce the top longitudinal joint,(3) when tunnel segment cracks, AFRP is used to reinforce the segment. At present, AFRP reinforcement for a shield tunnel is based on construction experience mostly. To provide the theoretical basis for AFRP reinforcement, a systematic study is completed to analyze the mentioned three aspects. The research contents and achievements are concluded as follows:(1) Based on a case of shield tunnel reinforced by AFRP, a three-dimensional numerical simulation model is built to analyze bearing behavior of reinforced and unreinforced whole-ring shield tunnel, with sufficient consideration of detailed structures including rubber gasket, cork rubber gasket and caulking. The results show that: the max reinforcement effect of AFRP is 11.43%. When the tunnel lateral deformation rate is between 1.10%-1.64%, AFRP reinforcement is effective. When the tunnel lateral deformation rate is above 1.64%, the reinforcement efficiency is not obvious. AFRP reinforcement shows optimal performance when the lateral deformation rate reaches 0.71%. The reasonable pasting layer is 2.(2) According to the above model, bearing behavior of reinforced and unreinforced tunnel longitudinal joint is deeply studied. The results indicate that: the max reinforcement effect of AFRP is 73.04%, and it is higher than the effect of AFRP reinforcement for a whole-ring shield tunnel. From the perspectives of limiting the total deformation of the joint and maximizing the reinforcement effect of AFRP, AFRP reinforcement should be done as early as possible.(3) Based on a case of tunnel segments reinforced by AFRP, a three-dimensional numerical simulation model is built to study deformation, stress and fracture characteristics of reinforced and unreinforced segment under various conditions. The results show that: segment deformation can be divided into three stages, including reverse deformation, small deformation and large deformation. Axial force can effectively improve flexural rigidity and anti-crack performance of segment. The max reinforcement effect of AFRP is 11.6%. AFRP reinforcement shows optimal performance when bending moment of segment under axial load of 700 kN reaches 210 k N?m. The reasonable pasting layer is 2.