Physical modeling of breaking wave induced pore pressure in a fine-sand seabed

Progressive waves may break while propagating towards shallow waters. Previous investigations on wave-induced seabed response mainly limit to regular waves, e.g., Airy linear waves and Stokes nonlinear waves. In this study, the breaking wave induced pore pressure in a fine-sand seabed was physically modelled in a wave flume. The breaking waves were generated by means of superimposing a series of large-wavelength waves onto the foregoing small-wavelength waves at a specified location. The vertical distribution of breaking wave induced pore pressure within the fine-sand seabed was measured with miniature pore pressure transducers for the three typical locations, i.e. at the rear, just under and in front of the wave breaking location. It was observed that before the event of wave breaking, the small-wavelength wave induced pore pressure was generally quite weak as expected. While the large-wavelength waves catching up with the small-wavelength ones, the superposed wave broke suddenly. The measured period of the pore pressure under the breaking waves is much larger than the wave period of the imposing large-wavelength waves. Nevertheless, the amplitude of the pore pressure under breaking waves gets smaller than that before the wave breaks; meanwhile, the values of wave height are greatly reduced after wave breaking.