Two-Dimensional Model for Accumulation of Pore Pressure in Marine Sediments: Fid-Bau Portal

Two-Dimensional Model for Accumulation of Pore Pressure in Marine Sediments

Jeng, D.-S. / Zhao, H. Y.

Abstract

A two-dimensional (2D) porous model was developed to investigate the accumulation of pore pressure in marine sediments in which the volume-averaged Reynolds-averaged Navier-Stokes (VARANS) equations were used as the governing equations for the wave motion and the Biot consolidation theory was used for the porous seabed. Unlike most of the previous investigations on the accumulation of pore pressure in which the amplitude of the shear stress over the wave period was used in the source term, in this study, the source term was redefined as a time-dependent function using the phase-resolved oscillatory shear stresses. Overall good agreement of both the oscillatory and residual pore pressures with previous analytical solutions and experimental data demonstrated the reliability of the model for the prediction of wave-induced pore-pressure accumulation. For the case with progressive wave loadings, the liquefaction zone related to the initial incident of the wave phases was formed as a 2D pattern during the first liquefaction wave period. This 2D pattern became one-dimensional after one wave period, decreasing progressively to a constant value after a number of wave cycles. For the case with standing wave loadings, a 2D liquefaction zone occurred first in the region where the shear strains are highest. Eventually, this 2D pattern becomes continuous, which implies that even the soil in the antinode section can be liquefied. Compared with the seabed response under linear wave loading, the pore pressure more easily accumulates to a higher value under nonlinear wave loading because of the higher peak in the shear strains. Parametric studies indicate that both the wave characteristics and soil properties affect the maximum relative liquefaction depth ( $z_{L} / h$ ) significantly. In general, the maximum liquefaction depth increases as the wave height and wavelength increase in shallow water within the seabed, which has a lower permeability and lower relative density.