Pore-water pressure response of a silty seabed to random wave action: Importance of low-frequency waves

Abstract

Wave-induced pore pressure in the seabed may cause seabed liquefaction and lead to geohazards such as submarine landslides. Under natural conditions, waves generally consist of different components with various frequencies, and the seabed response to each wave component can vary considerably. However, little is known concerning these differences. In this study, a series of flume experiments were conducted to investigate the pore pressure responses in a silty seabed to various components of random waves. According to the experimental results, the short wave (SW) component had high energies, but the SW-generated high-frequency hydrodynamic pressure (HF p0 ) decayed rapidly in the seabed. The long wave (LW) component had low energies, but the LW-generated low-frequency hydrodynamic pressure (LF p0 ) was effectively propagated in the seabed. The transmittance coefficient of the low-frequency pore pressures (LF p ) was two times that of the high-frequency pore pressures (HF p ). The energy ratio of LF p /HF p was enhanced with increasing soil depth, and the energy of LF p was greater than that of HF p at soil depths ≥15 cm, indicating that the contribution of LWs to the cumulative pore pressure is enhanced with an increase in soil depth. An important implication of our findings is that the use of statistical wave parameters (e.g., significant wave height and average wave period) to determine pore pressure responses of the seabed can underestimate liquefaction risk, and in turn, lead to unsafe engineering designs. • Long wave component generates significantly stronger pore pressure. • High-frequency pore pressures propagated poorly in the seabed. • Low-frequency pore pressures readily propagated within the seabed. • Long wave component had significantly larger contribution to deep soil pore pressure.