Study On The Influencing Factors Of Instantaneous Subsidence Of Artificial Reefs In The Seabed Based On ABAQUS

Artificial reefs are underwater structures that are deliberately placed on the seabed.Affected by impact load and self-weight load,artificial reefs will undergo instantaneous subsidence on the seabed when they are deployed,resulting in a decrease in the usable volume of artificial reefs and affecting the function of artificial reefs.However,most of the current research on the settlement of artificial reefs are the surveys of the results,and few studies have carried out the settlement estimation.Therefore,based on the finite element analysis software ABAQUS,this thesis carried out a numerical simulation of the settlement process of the cube-framed artificial reef,and systematically studied the dynamic process of the artificial reef release stage by theoretical analysis and physical model experiment,and explored in detail the factors affecting the instantaneous subsidence of artificial reef in the seabed from multiple dimensions.The research results can provide scientific reference and reasonable suggestions for the structural design of artificial reefs,site selection,and deployment process,in order to reduce the settlement of artificial reefs in the initial stage of deployment and maximize their effectiveness.The specific research work and conclusions are as follows:(1)Based on the dynamics formula and the soil bearing capacity formula,the differential equations describing the dynamic process of artificial reefs falling freely in seawater and velocity-displacement and energy-displacement when sunk into the soil are derived.(2)In the model test,the impact velocity at the moment of contact between the artificial reef and the seabed was controlled by changing the free release height,and the settlement of the artificial reef at the corresponding impact velocity was obtained.The error between the experimental results and the simulation results is 10.8%,which verifies the feasibility of the numerical simulation method.(3)Based on ABAQUS,it is found that the instantaneous subsidence of artificial reefs in the seabed is closely related to the spatial configuration of artificial reefs.The maximum settlement rate of the artificial reef is positively correlated with the opening ratio in the reefbottom,volume ratio and incident angle,and these factors have a linear function relationship with the maximum settlement rate.On the premise of ensuring the biological effect of the artificial reef,a smaller opening ratio and a smaller volume ratio can be selected;the structural design of anti-overturning should be increased as much as possible to avoid large incident angle.(4)Based on ABAQUS,it is found that the instantaneous subsidence of artificial reefs in the seabed is closely related to the mechanical properties of the seabed soil.Within a certain range,the maximum settlement rate of the artificial reef is negatively correlated with the elastic modulus of the soil,the Poisson’s ratio of the soil,the internal friction angle and the cohesion,and there is basically a secondary function relationship between these factors and the maximum settlement rate.It shows that when selecting the site for an artificial reef,the physical and mechanical properties of the seabed soil should be considered,and sea areas with high elastic modulus,Poisson’s ratio,internal friction angle and soil cohesion should be selected as much as possible.When there is not much difference in elastic index,internal friction angle and cohesion can be used as priority reference factors.(5)Based on ABAQUS,it is found that the flow velocity in the sea floor affects the maximum settlement of artificial reefs.Under normal current conditions,the wave-current coupling force has little effect on the subsidence,but under the condition of extreme flow velocity(over 1.0 m/s),the subsidence of the artificial reef will continue to increase after undergoing instantaneous subsidence.In the site selection stage of artificial reef arrangement,the flow velocity in the selected sea area should not exceed 1.0 m/s as much as possible.If it exceeds this value,relevant anti-subsidence measures should be taken.