Experimental And Numerical Studies Of Seabed Response To The Wave-induced Movement Of Marine Structure

With the proposal of my country’s the Belt and Road development strategy,the construction of offshore structures is particularly important,such as submarine immersed pipes,cross-sea bridges,offshore drilling platforms,etc.The offshore structures and the underlying seabed are subjected to complex cyclic loads throughout the year,causing the pore water pressure of the seabed to increase,the effective stress is reduced,the shear resistance of the seabed is reduced,or the direct liquefaction causes the seabed to instability,causing the catastrophe of the marine structure.Cyclic load waves have the most prominent effect on the stability of structures,mainly because waves directly act on the surrounding seabed of the structure or waves act on the structure,generating overturning moments,causing the structure to wave motion.However,the problem of seabed liquefaction under the action of structure wave motion is rarely reported.It can be seen that exploring the dynamic response of the seabed under the wave motion of marine structures not only provides guiding opinions on the development of offshore structures,but also enriches the theory of seabed liquefaction.In this study,the dynamic response of the seabed under the action of wave motion of marine structures is the research object,and the research and discussion are carried out through the methods of experiment and numerical simulation.Mainly based on the flume experiment,a mechanical device that can be used to simulate the wave motion of structures was developed,revealing the influence mechanism of wave motion characteristics,seabed characteristics,and structural characteristics on seabed pore water pressure;subsequently,based on the second COMSOL Develop technology and establish a numerical model of the nonlinear cumulative response of seabed pore pressure under the action of structure wave motion;through physical experiments and numerical simulation methods,clarify the mechanism of seabed liquefaction caused by structure wave motion.The specific research content and conclusions of this article mainly include the following three points:1.The symmetrical structure model of the power plant was pulled to simulate the response of seabed pore pressure under the action of regular wave motion,the effects of sand bed characteristics,structural characteristics,wave-induced vibration characteristics,etc.on the excess pore water pressure in the seabed are discussed separately.The analysis of seabed liquefaction under wave motion is given.The results show that the smaller the particle diameter is,the more obvious the accumulation and dissipation of excess pore water pressure is;the more obvious the dead weight is on the accumulation and transient changes of excess pore water pressure;the amplitude of the wave-induced vibration increases or decreases periodically.Small,the accumulation of excess pore water pressure and the depth of liquefaction increase significantly;the magnitude of the accumulation of excess pore water pressure at the bottom of the ocean structure near the middle area is larger than that in the end area.2.The pore pressure response of the seabed under irregular wave motion is simulated by the power plant tow the asymmetric structure model.The results show that with the decrease of the structural factor of the asymmetric model,the cumulative response of the excess pore water pressure in the seabed is that the middle part is greater than the two ends,the low amplitude end is greater than the high amplitude end,and the transient response amplitude increases with the end amplitude.But increase;the transient response and liquefaction of the lower seabed of the random motion model are affected by the intensity of motion,and the early stage in the deep seabed is mainly the residual response.3.The secondary development technology of COMSOL software is used to establish a structure-seabed-fluid coupling model.The cumulative response of the pore pressure in the porous media seabed is calculated by solving the Boit consolidation equation and the semielastic and semi-empirical nonlinear cumulative equation of the seabed.Studies have shown that the excess pore water pressure gradually accumulates and then tends to a stable value;the cumulative pore water pressure in the depth direction of the coastal bed first increases and then decreases;the cumulative value in the middle of the structure is larger than the surroundings;the cumulative value of the pore pressure increases with the saturation of the seabed,The shear modulus and permeability coefficient decrease with the increase of the amplitude of the wave-induced vibration and the period decreases;the depth of liquefaction increases with the increase of the amplitude and decrease of the period.