A new elasto-plastic method for analyzing wave-induced dynamic behaviors of seabed was proposed by combining linear wave theory, the Biot's consolidation theory and the sand constitutive model by Zhang's research group, which is capable of reproducing the pre- and post-liquefaction behaviors of soil. This method was first validated by Miyamoto et al.'s experiment. Then, numerical simulations were conducted to investigate interaction of pipeline and seabed under dynamic loadings, showing the distribution of liquefaction in the seabed is significantly influenced by the pipeline, both the wave- and earthquake- induced excess pore pressures accumulate and fluctuate but with different rates and amplitudes.
In the ocean environment, the interaction of pipeline and seabed as well as the occurrence of soil liquefaction around the pipeline under dynamic loadings like earthquakes or waves is the main threat to the stability of pipeline. ASCE (1966) also pointed out that pipeline flotation in saturated sandy seabed under dynamic loadings would probably lead to pipeline destruction.
To date, many research on the interaction of pipeline and seabed under dynamic loadings, e.g., ocean waves, is based on the assumption that the seabed is a poro-elastic material, e.g., MacPherson (1978) and Damgaard et al. (2006), which only taking the influence of upward seepage forces on the pipeline into consideration.
The seabed is an elasto-plastic material in realistic ocean environment under earthquakes or relatively large waves, then the constitutive model PZ±V (Pastor et al., 1990) is generally adopted in the analysis of earthquake- or wave-induced soil liquefaction, and even in the interaction of pipeline and seabed under dynamic loadings (Dunn et al., 2006). The PZ±V constitutive model is capable of simulating loading and unloading behavior of sand under cyclic loading, however, it can not reflect the influence of soil harding and consolidation, meanwhile it has limits in the post-liquefaction behavior of soil (Ye et al., 2013).
