Experimental Study of the Waves-Induced Flows Inside a Liquefied Silty Seabed

Silty seabeds are widely distributed around the world and liquefy easily under periodic wave loads, which may significantly affect wave motion and soil dynamics. Laboratory experiments have been conducted to study the wave-induced flows inside the silty seabed, as well as the wave-induced soil dynamic and wave kinematics. Silt particles with a median diameter of 0.06mm are selected to model the seabed, and in the seabed preparation, the Froude-Cauchy similarity criterion is required to satisfy. The free surface elevation, excess pore pressure, and soil motion velocity are measured to study the wave motion and the flow dynamics over and inside the seabed. The experimental results show that: (1) Liquefaction in the silty seabed contributes to a rapid wave damping, manifested as a significant decrease in wave height; (2) Liquefaction occurs when the accumulated pore water pressure in the silty seabed exceeds the vertical initial effective stress. The liquefaction depth develops in a top-down manner; (3) The flow velocity inside the seabed varies periodically. The dimensionless horizontal velocity component of the soil particles in the liquefied seabed is smaller than the vertical velocity component but has a longer period; (4) The instantaneous velocity field of the liquefied soil particles reaches its peak when the water-mud interface moves to the lowest or highest point. When liquefaction just occurs, the instantaneous velocity field is likely to be disturbed by the discharge of bubbles from the unsaturated seabed.