Mechanical and Failure Characteristics of Shear Keys on Immersed Tunnel Segment Joints under Differential Settlements

In order to research mechanical and failure characteristics of shear keys on immersed tunnel segment joints, a 1:4.69 large scale immersed tunnel physical model test was conducted on a settlement platform. Bending and twisting working conditions of segment joints caused by uneven settlements and uneven back-silting were simulated, by means of controlling the lifting jacks under the settlement platform. Simultaneously, a 3-D numerical simulation which considered the nonlinearity of rubber pads and contacting effects between segment joints was carried out. The results shows that vertical shear keys have main contribution to resist expansion of segment joints in bending condition, and vertical shear keys on the soft layer have larger shear forces than that on the hard layer. In addition, shear stresses were mainly concentrated at the terminal corners and connecting corners between shear keys and segments. Correspondingly, at the terminal corners and connecting corners between shear key and segments appeared 30° ∼60° and 45° extending cracks respectively. At last, some structural strengthen suggestions on shear keys were offered for immersed tunnel design.