A 3D FEM model is proposed and verified with existing experimental data for simulating wave-induced transient and residual pore pressure responses around a pile foundation. The numerical results show that the residual pore pressure tends to be amplified at the bottom of the pile foundation; near it, this pressure increases and the amplitude of transient pore pressure decreases with the decrease of soil permeability. The wave nonlinearity affects both transient and residual pore pressures around the pile. The effect of the pile diameter on the oscillatory pore pressure is much more obvious than that on the buildup of pore pressure. The liquefaction zone around the pile is asymmetric; the maximum liquefaction depth appears at the back of the pile foundation.
Piles have been widely used for the foundations of coastal and offshore structures, such as platforms, long-spanning bridges, offshore wind farms, etc. Under the action of ocean waves, pore water pressure may be induced in the seabed around pile foundations, which is usually accompanied by the reduction of effective stresses. In some extreme conditions, such as hurricanes or storms, the soil around the pile foundation may be liquefied, resulting in large displacements of the pile foundation and the eventual collapse of upper structures. Thus, a proper evaluation of wave induced pore pressure responses and soil liquefaction around the pile foundation is crucial for the geotechnical design of maritime structures. Generally, there are 2 significant mechanisms for wave-induced pore pressure responses, which are also observed in laboratory experiments and field measurements (i.e., Nago et al., 1993). The first mechanism, termed transient or oscillatory pore pressure, is characterized by the attenuation of amplitude and the phase lag within the seabed. Since the 1970s, wave-induced pore pressure responses and liquefaction within a porous seabed have gradually concerned marine geotechnical engineers and researchers.