Study On The Thickness Of Wave-induced Liquefaction Of Submarine Silty-bed In Yellow River Delta

There have been a lot of research achievements on the dynamic response of the seabed and the seabed instability under wave loadings. When the seabed is liquefied, the liquefied soil can move like the fluid, the liquefied soil with this motion state will directly affect a large number of development activities in this area, for example, producing an additional pressure on the buildings leading to a large damage, such as oil exploration, etc. Series of researches are carried through this paper based on these engineering geological facts.In this paper, the silty soil in Yellow River delta was the main research object. Based on the acknowledgment of ocean dynamics and geology conditions of Yellow River Delta, trough physical tests and numerical simulations, this paper mainly studys on wave-induced liquefaction, and what conditions influences the depth of the liquefaction.The Viscosity of silty-soil liquid equals to the internal friction at macro performance, when it is liquefied. So, the soil, which is sampled at Yellow River subaqueous Delta, interfacial friction between the two soil calys is studied to provide a basis support for energy dissipation in this paper. Secondly, through the flume test, the progressive liquefied model is found, and,the depth of the liquefaction is measured under the condition of different wave heights in liquefied bed and no-liquefied bed. Thirdly, Based on Lamb’s two-layer fluid theory, a interfacial wave model is introduced to figure up the depth of liquefaction, and compare with the physical result.The results showed that the interfacial friction increased with less clay content, and decreased with more clay content, and the number of maximum friction is ranged from 3.76kPa-5.12kPa. The friction showed a significantly difference in moisture content, and the difference increases with the decreases in moisture content. When changed the shear rate, the interfacial shear strength increases with the increasing of shear rate, but the interfacial friction is not almost changing. It is on the same law with viscosity. Therefore, the value of the interfacial friction is used to be replaced the viscosity in theoretical calculation.The progressive development of liquefaction is observed in the flume test. The depth of silty-soil seabed is gradual development downstairs with time, when it comes to the deepest location, it is upstairs with time, apparently with layer phenomenon; it is find that the depth of liquefaction increase with wave height’s increasing.Combined with measured friction and observed the top-down gradual development mode of liquefaction, solving the wave theory of double fluid model is derived, using the finite difference method, the Matlab program, using the effective stress principle explanation theory analyzes the seabed liquefaction depth of liquefaction, verified, the theoretical results with the test and the correction coefficient is 0.58 between the measured data. And compare the different water depth and thickness of seabed on the depth of the seabed liquefaction, the influence of thickness of seabed within 0.2 times the wavelength, the depth of liquefaction is almost equalto the thickness of seabed; Seabed liquefaction depth with the increase of the depth of the water, increase after the first decreases, and in the depth of the water between 9 to 10 m,attain to the maximum depth of the seabed liquefaction.