Effects of siltation and desiltation on the wave-induced stability of foundation trench of immersed tunnel

The evaluation of stability for the submarine artificial slope is important in the construction of offshore structures such as immersed tunnels and embedded pipelines. The siltation in marine dynamic environment is common, inevitable, but difficult to deal with. Cohesive sediment, or mud, is encountered in most water bodies throughout the world, and thus siltation inevitably occurs in the stage of underwater excavation for the offshore structure foundations. To this end, based on the temporal and spatial variations law of siltation observed from the trial trench in-situ test of Shenzhen-Zhongshan Link in China, a numerical study is carried out on the influences of siltation and desiltation on the stability of foundation trench slope under wave action. The waves are simulated by the Reynolds-Averaged Navier-Stokes (RANS) equations and then applied on the surface of seabed and trench slope. The pore pressure induced by the wave action is obtained by Darcy's law. The seabed is characterized by Mohr-Coulomb constitutive model and the factor of stability (FOS) of the slope is calculated using the strength reduction method. Three failure modes are assumed to analyze the stability of trench slope and to determine the most unstable mode. A sensitivity analysis is conducted on various key factors affecting the whole stability of the trench slope after siltation or desiltation, which is valuable for practical engineering design. •An integrated FEM model is proposed to analyze the wave-induced slope stability of the temporary trench of immersed tunnel.•The wave-induced seepage pressure near the slope is determined by Darcy's law and considered as external load.•The FOS for the most dangerous situation is regarded as the stability index in the whole process of dynamic wave action.•Three failure modes are analyzed to determine the most probable instability mode of trench slope.•Effects of seabed siltation and desiltation on the wave-induced slope stability are investigated.