Mechanical Performance and Experimental Research on Plug-in Fast Connector of Shield Tunnel

Urban development and renewal reduce the performance of shield tunnels and may cause structural safety hazards. Thus, a new plug-in fast connector is developed for shield tunnels to improve structural resilience. The connector does not require additional tightening, and the segment opening and dislocation are small. Taking a 650 mm thick segment as the prototype, this paper conducts the tensile and shearing tests of the plug-in fast connector, to investigate the structural form, material properties, and the force transmission between the connection and concrete segment. In addition, the theoretical value of the connector is employed to compare experimental values. The main conclusions are as follows: (1) The insufficient bond strength between the embedded sleeves and concrete causes the fast connector to be pulled out and the tensile failure of concrete is occurred. (2) The yield strength of the connector is about 150 kN, and the failure strength is about 200 kN, which is slightly lower than the design value. (3) With the increase of the shearing displacement, damage occurs inside the embedded sleeves and then the concrete of the upper surface is crushed. Finally, the tightness between CR and sleeves is invalid and the shear strength of each connector is 210 kN. (4) The shear stiffness of the plug-in fast connector is fitted by two straight lines, and K1 and K2 are 2.611 kN/mm and 18.544 kN/mm respectively. (5) The new plug-in fast connector can improve the longitudinal mechanical performance of a shield tunnel. The subsequent research should focus on the selection of materials for embedded sleeves and the bond strength between the sleeve and concrete.