Detailed knowledge of the wave-induced pore pressure in a poroelastic seabed is important for marine geotechnical and coastal engineers involved in the design of offshore installations. To simplify the complicated problem, most previous investigations have only concerned with ocean waves propagating over an isotropic seabed with uniform soil characteristics, ignoring the effects of anisotropic soil behavior and variable soil characteristics. This paper proposes a finite element model to investigate the wave-induced pore pressure in a cross-anisotropic seabed of finite thickness with variable Young's modulus and permeability. The numerical results indicate that the effects of anisotropic soil behavior, variable Young's modulus and soil permeability on the wave-induced pore pressure are significant.
The evaluation of the wave-induced pore pressure has been recognized as one of key factors that must be taken into account in the analysis of seabed instability. It has been submitted that gravity waves propagating over the ocean exert significant dynamic pressure on the sea floor in shallow water. These pressure fluctuations further induce variations of excess pore pressure in non-cohesive marine sediments. Once the upward seepage forces generated by excess pore pressure become greater than the self-weight of soils, a sedimentary bed may be liquefied, leading to seabed instability. This is the reason why this problem has attracted more attention from marine geotechnical and coastal engineers in recent years. In general, marine sedimentary seabeds display some degrees of anisotropy, with different elastic properties in different directions owing to the mode of their deposition, particle shape and stress history. However, most marine sediments show more limited forms of anisotropy. A cross-anisotropic material is one of the examples, which has same properties in all horizontal directions, but different properties in the vertical direction. Unlike an isotropic material, the elastic behavior of a cross-anisotropic material is dominated by five independent elastic parameters (Pickering, 1970).
