Experimental study of soil liquefaction and wave damping during nonlinear waves and silty seabed interaction

Silty seabeds are highly susceptible to liquefaction under cyclic wave loading. Such liquefaction, in turn, can significantly impact wave propagation and soil dynamic responses. In this study, a series of laboratory experiments was conducted to investigate wave propagation and soil behavior during wave–seabed interactions. The seabed consists of silt with a mean grain size of 0.032 mm, and the incident waves are periodic. Free surface elevation, wave–induced pore pressure, and soil velocity are measured using wave gauges, pore pressure transducers, and a Particle Image Velocimetry (PIV) system, respectively. Analysis of the measurements shows that under certain nonlinear wave actions, pore pressure can exceed the initial vertical effective stress, which leads to the wave–induced residual liquefaction within the silty seabed. Wave height dissipates quickly as waves propagate over a liquefied seabed, and the dissipation rate depends strongly on the depth of liquefaction. When residual liquefaction happens, the water–seabed interface oscillates with the wave, and the period of soil motion velocity is consistent with the wave period. Results also show that a phase difference exists between soil and wave motion. The phase lead angle of soil motion velocity gradually increases with soil depth. Additionally, compared with the analytical solutions, the liquefied silt behaves like a viscoelastic fluid. Due to the nonlinearity of both wave and mud viscosity, errors may occur in estimating soil velocity magnitude and phase angle with linear analytical solutions.