A Strain-Based Procedure to Screen for Wave-Induced Pore Pressure Generation in the Seabed

Abstract

This manuscript presents a strain-based procedure to screen for wave-induced residual pore pressures in the seabed. The generation of residual pore pressures can lead to instabilities and/or liquefaction within the seabed producing undesired consequences in the marine environment. Currently, techniques to predict wave-induced liquefaction are governed from seismic-based principles; however, differences between these two contrasting mechanisms (earthquakes and ocean waves) creates uncertainties within the soil relating to: the determination of an equivalent number of loading cycles representing the irregular time history of ocean wave loading, the prediction of cyclic resistance at low levels of effective stress (i.e. in near-surface sediments), and pore pressure generation in silty/clayey soils. First, the strain-based model is described. Linear elastic finite element analyses are used to develop normalized charts for estimating the cyclic shear stresses in an inhomogeneous seabed. The model is validated from existing wave tank experiments on silt. This comparison showed the generation and non-generation of excess pore pressure corresponded to factors of safety less than and greater than one respectively. Lastly, a case study is presented to illustrate the practical implementation of the model.