Study on characteristics of dynamic stress path of finite-thickness seabed under standing waves

Based on the analytical solutions for standing wave-induced soil response in the finite-thickness seabed, the dynamic stress path of soil element is deduced in the stress plane with half of the axial deviation stress on the horizontal axis and shear stress on the vertical one. The results of the analysis show that the dynamic stress path of the soil element located at the nodes is a line segment on the vertical axis, that located at the antinodes is a line segment on the horizontal axis, and that at other locations is non-standard ellipse. Taking the North Sea as an example, the initial phase difference (), half of the amplitude of the axial deviation stress (a) and the amplitude of the shear stress (b) are analyzed. It is shown that when the soil element is located between the node and the antinode, the dynamic stress path approaches a line segment with the depth of 0 ~ 0.35 times the thickness of seabed, while with the depth of 0.35 ~ 1 times the thickness of seabed, it is a non-standard ellipse, and the value of varies along the relative depth in the range of -180 ° to -150°. Additionally, the influences of permeability of seabed, wave period and thickness of seabed on dynamic stress path are analyzed. The results indicate that the change of the coefficient of permeability and wave period do not alter the values of a and b, but the value of is affected. When the coefficient of permeability of seabed is larger than 10^-2 m/s, the dynamic stress path of the soil elements is a line segment in the whole of seabed. And the value of changes in the range of -180 ° to -150 ° when the seabed is under different wave periods. Moreover, the dynamic stress path approaches a line segment with the depth of 0 ~ 0.03 times the wavelength when the thickness of the seabed is thinner. When the thickness of the seabed is in the range of 0.3 ~ 2 times the wavelength, the surface area where the stress path is a line segment increases with the increase of the thickness of the seabed.