A dual mortar method for analyzing the effects of wave-induced instantaneous liquefaction on an immersed tunnel with a liquefaction-associated non-Darcy flow model

Engineering practices have illustrated that ocean waves can cause non-ignorable deformations in immersed tunnels and the surrounding seabed. Under extreme wave conditions, instantaneous liquefaction of the seabed can occur, leading to a decrease in the bearing capacity of the seabed and potential damage to subsea structures. The liquefaction-associated non-Darcy flow model, previously proposed to eliminate the nonphysical tensile behavior of the seabed, is incorporated into a wave–seabed–tunnel model, which introduces special interfacial conditions between the seabed and the immersed tunnel. These interfacial conditions are numerically treated by developing a dual mortar method, which also permits using nonconforming meshes between the seabed and the tunnel. This model is applied to investigate the wave-induced response of an immersed tunnel fully buried in a non-cohesive seabed. The representative values of wave parameters are obtained by analyzing in-situ monitoring data from coastal stations, and then used as the input of the wave–seabed–tunnel model. The numerical results show that extreme waves can pose significant influences on the immersed tunnel.