With the increasing of extreme weather events, more attention has been drawn to the protection of coastal structures. Wave-induced seabed instability is a major factor that may damage the coastal structures. In this paper, a 2-D quasi-dynamic u-w-p model is developed to examine different seabed behavior under different wave actions. Further, this paper aims to acquire a better understanding of the soil failure process, which will be able to reduce the possible damage of coastal structure caused by extreme weather events. In u-w-p model, acceleration, velocity, and displacement terms are considered separately for both solid and fluid phases. The u-w-p model also can be simplified based on actual condition. The governing equations of u-w-p model are deduced from constitutive law and conservation law under certain assumptions. The numerical solutions are developed by using finite difference method (FDM) and three major factors (pore water pressure, effective vertical stress and shear stress) are outputted from the models as major analysis target. The result shows that both liquefaction and shear failure have low potential to occur in clayey seabed, this may caused by the dense soil structure and low permeability of clay. The pore water pressure vary linearly according to the depth, however, this variation is not significant in clayey seabed (with 6.4% decrease from the surface to bottom). In addition, there is no phase lag in clayey seabed. The excess pore water pressure will not accumulate quickly and reach a massive value inside the clayey seabed.