Mechanical and waterproof performances of joints of shield tunnels with large cross-section under earthquakes

In order to study the mechanical and waterproof performances of joints of large-section shield tunnels under seismic conditions, ABAQUS is used to establish a 3D stratum-structure finite element model and a 2D sealing gasket finite element solid model. The mechanical properties, offset, and openings are studied for the segmental joints. Based on the deformation results of the joints at different positions, the deterioration of the waterproof performance of the tunnel is discussed. The results show that: (1) The maximum principal tensile stress of the joints at the lower part of the arch waist under moderate and large earthquakes exceeds the maximum tensile strength of concrete, leading to damage on the concrete. (2) The size of longitudinal joints keeps basically the same under different earthquakes, and their distribution is like a "glass" shape. The amount of misalignment between the arch top and the arch bottom is relatively small, while the amount of misalignment at the arch waist and arch feet is relatively large. (3) The joints at the right side of the dome have the best waterproof capacity of 2.77 MPa, which is only 16% weaker than that under the normal situation. The waterproof performance is severely weakened by 40% at the joints near the arch waist.