Numerical simulation of the wave-induced dynamic response of poro-elastoplastic seabed foundations and a composite breakwater

In this study, an integrated numerical model FSSI-CAS 2D (previously known as POROWSSI 2D) is developed for the problem of wave-elasto-plastic seabed-structure interactions, where the Volume Average Reynolds Average Navier–Stokes (VARANS) equation is taken as the governing equation for wave motion and porous flow in porous medium; the dynamic Biot’s equation known as “u-pu-p” is taken as the governing equation for the dynamics of porous seabed soil under wave loading. The Pastor–Zienkiewicz Mark III proposed by Pastor et al. (1990) [45] is used to describe the dynamic behaviour of poro-elasto-plastic seabed under wave loading. This developed integrated numerical model is validated by a centrifuge test conducted by Sassa and Sekiguchi (1999) [30]. The developed integrated numerical model is applied to investigate the wave-induced dynamic response of a composite breakwater and its elasto-plastic seabed foundation. The numerical results indicate that the pore pressure in an elasto-plastic seabed builds up under wave loading, leading to the reduction of the contact effective stresses between soil particles. The residual liquefaction occurs when the effective stresses decrease to a value approaching zero. The wave-induced residual liquefaction in seabed is progressive downward. A parameter considering the cohesion and friction angle of soil is defined to evaluate the residual liquefaction potential. Analysis results illustrate that the friction angle of soil has significant effect on the soil liquefaction; and Nevada dense sand becomes liquefied if the defined parameter exceeded 0.86. Parametric study shows that wave characteristics and soil properties have significant effects on the wave-induced progressive residual liquefaction in loose elasto-plastic seabed foundation.