A Numerical Approach to Determine Wave (Current)-Induced Residual Responses in a Layered Seabed

Wave-induced pore pressure in marine sediments has attracted great attention from geotechnical and coastal engineers over previous decades; however, the evaluation of wave (current)-induced residual soil liquefaction in a porous seabed with multiple sublayers has not been attempted theoretically. Because of the rapid accumulation of sediment and the complex hydrodynamic environment, the deposits in the Yellow River Delta always have large-scale and long-term instability. This study proposes a simple but workable elastoplastic approach for obtaining solutions for the residual pore pressure and liquefaction potential in a noncohesive-layered seabed subjected to water waves and current in the Yellow River Delta. Based on a numerical model that was validated with previous laboratory experiments, the influences of soil characteristics on pore pressure are examined. Special attention is given to the effect of replacing an existing layer with a coarser material as a top layer for protecting the underlying sediment from liquefaction. Numerical results show that the development and distribution of the residual pore pressure and liquefaction are obviously affected by the multilayer distribution of the seabed that is ubiquitous in the actual seabed. Moreover, the influence of the ocean current on the residual pore pressure and liquefaction depth, which is mainly concentrated on the upper sublayer of the multilayered seabed, is also significant. Furthermore, coarse materials with sufficient thickness can be used as the replacement layer to restrain the residual liquefaction efficiently and to improve stability of underlying fine layers.