Characteristics of Interfacial Waves Over a Liquefied Seabed and Their Effects on Sediment Suspension

Abstract

Wave‐induced seabed liquefaction can enhance coastal sediment suspension, but the wave‐cycle‐scale influence of interfacial‐wave motion remains poorly understood. Wave‐flume experiments were conducted on a silty bed under two regular‐wave conditions to compare near‐bed hydrodynamics and sediment suspension between a non‐liquefied condition and a liquefied condition. Under the non‐liquefied condition, suspended sediment concentration (SSC) exhibited a double‐peaked intra‐wave pattern and generally varied with turbulent kinetic energy and Reynolds shear stress, suggesting predominantly shear‐related suspension. After liquefaction, sustained interfacial waves developed at the mudline, with a root‐mean‐square amplitude of approximately 1.4 cm. Around the onset of sustained interfacial‐wave motion, near‐bed SSC increased from approximately 1.3 to 2.6 g L ⁻¹ within 4–5 wave cycles, the intra‐wave SSC distribution shifted to a single‐peaked pattern, and its relationship with Reynolds shear stress weakened. During rapid mudline descent, upward turbulent sediment transport was strongest and accounted for approximately 93% of the positive cycle‐integrated turbulent sediment flux. Under the experimental conditions examined, these observations suggest that interfacial‐wave motion may provide an additional phase‐dependent mechanism modulating sediment suspension over a liquefied seabed, offering a physical basis for improving the representation of sediment transport over liquefied beds.