Session: 06-02-01 Coastal Engineering I

Paper Number: 127536

127536 - Experimental Study of the Waves-Induced Flows Inside a Liquefied Silty Seabed 

Experimental study of the waves-induced flows inside a liquefied silty seabed

Ning Chen^1,2, Linlong Tong^1,2,*, Zhen Huang^1,2, Chen Yang^1,2, Jisheng Zhang^1,2,*

1 Key Laboratory of Ministry of Education for Coastal Disaster and Protection, Hohai University, Nanjing 210098, China

2 College of Harbor, Coastal and Offshore Engineering, Hohai University, Nanjing 210098, China

*Corresponding e-mail address: tllnj@hhu.edu.cn; jszhang@hhu.edu.cn

  Silt coasts are widely distributed over the world. Under a wave loading, the silty seabed experiences complex changes in pore water pressure, stresses, and displacement. Since the permeability of silty seabed is poor, the pore water is difficult to drain out. As a result, the pore pressure may build up to cause liquefaction inside the seabed. In the past decades, wave-induced liquefaction mechanisms and their effects on wave motion have been extensively studied. However, the wave-induced flows inside the seabed are still desired to investigate, as they may have significant influences on sediment transportation.

  In this study, a series of experiments are conducted in a wave flume to study the wave-induced flows inside the silty seabed. 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. In the experiment, the free surface elevation, wave boundary layer velocity, pore pressure, soil motion velocity, and shear modulus of the soil are measured to study the wave motion and the flow dynamics over and inside the seabed. During the experiment, silt particle suspension, water-seabed interface oscillation, and liquefied layer motion are observed, when the seabed liquefied. The flow velocity inside the seabed is by the PIV method. The results show that: (1) Liquefaction occurs when the accumulated pore water pressure in the silty seabed exceeds the vertical initial effective stress. The soil significantly softens during liquefaction; (2) The instantaneous velocity field of the liquefied soil particles reaches its peak when the water-mud interface displacement is equal to 0.

Presenting Author: Ning Chen Hohai University

Presenting Author Biography: Chen Ning, graduated from Hohai University in 2017 with a bachelor's degree. Now she is a doctoral student at Hohai University, majoring in Harbour, Coastal and Offshore Engineering. Her main research focus is on the mechanism of wave-seabed-structure interaction. Currently, she is committed to studying the coupling response mechanism of random waves, mound breakwater, and silty seabed. She has received honors such as Outstanding Student of Hohai University and Charming Graduate of Hohai University. She has been awarded the first-class scholarship for doctoral students multiple times. She won the first prize at the 7th Graduate Forum of the Jiangsu Society for Oceanology and Limnology in 2022.

Authors:

Ning Chen Hohai University
Linlong Tong Hohai University
Zhen Huang Hohai University
Chen Yang Hohai University
Jisheng Zhang Hohai University