Deformation characteristics of joints of immersed tube tunnels under coupling loads of back silting - tidal cycle

The proposed method focuses on the deformation characteristics of joints of immersed tube tunnels under cyclic load coupling. By establishing the tunnel-soil interaction model, the tunnel is simplified to the Timoshenko beam model, and the foundation is simplified to the Kerr foundation model. At the same time, considering the change of the subgrade coefficients with time, the theoretical model for the element-joint is established to analyze the transfer angle and deflection of the joints. By comparing the joint deformations of immersed tube tunnels under two different loading modes, namely load superposition and load coupling, the contribution proportion of structural deformation caused by back silting loads in the total deformation is discussed, and a theoretical analytical method suitable for analyzing the joint deformations during operation and maintenance is proposed. A comparison with the numerical results of ABAQUS demonstrates the applicability of the proposed method. By comparing with the measured data of Yongjiang immersed tube tunnel, it is shown that the dynamic response of the immersed tube tunnel is significantly affected by the cyclic load coupling, which is greater than the superposition of structural deformation caused by the single load. The deformation of immersed structure caused by the back silting loads accounts for 75%~125% of the deformation caused by the cyclic load coupling. The proposed theoretical model can well analyze the measured settlement results, which verifies the validity of the proposed theoretical model.