A 3D numerical model for the sea bed response under free surface water waves is constructed. Free surface is modeled by Volume of Fluid (VOF) method and water wave is generated by numerical wave maker boundary condition. An iterative numerical scheme is proposed to solve Biot consolidation equation using finite volume method (FVM). The coupling between water wave and sea bed is through pressure and stress condition on common boundaries. Numerical test shows good agreement with analytical solution. 3D application of sea bed response under waves with the presence of object is also carried out to investigate the liquefaction potential.
The interest in wave-seabed-structure interaction is growing because it is important for geotechnical engineers to design offshore engineering projects (such as pipe lines, piles and break waters). Also sinking/floating of objects on the sea bed (such as wrecked ships, mines) is closely related to the sea bed response under waves. Many experiments (Sakai et al, 1994; Sumer et al, 1999) and numerical simulations (Magda, 1996; Jeng and Lin, 1999; Gao et al, 2003) have been done to try to understand this complicated process. There are also many analytical models which describe the sea bed response and give fairly good results (Yamamoto, 1977; Mei and Foda, 1981; Jeng and Hsu, 1996; Yuhi and Ishida, 2002). But most of the models just assume the wave pressure on the water-bed interface using wave theory. This is applicable as a first order approximation for many cases if there is only water wave and sea bed interaction. But for the case when there is extra object in the system (such as pile, semi-buried foundation, etc.), the water flow around the object will be highly three dimensional and is not easy to get an analytical solution from wave theory.