Initial Penetration Depth Analysis And Stability Study Of Artificial Reef

As the main technical means of Marine pasture construction,artificial reef is widely used in the world.There are some stability problems in artificial reef,such as overturning,slipping,settling and scour.Among them,serious settlement will affect the space effective utilization rate and service life of artificial reef.In order to reduce the influence of artificial reef settlement,scholars of various countries have proposed many solutions by analyzing the influence of tidal current,wave,seabed bearing capacity,artificial reef structure and stacking density on artificial reef settlement.However,most scholars have considered the settlement caused by the artificial reef after being placed for a long time,and few have explored the influence of the initial penetration depth of the artificial reef after the free fall on the artificial reef.The initial penetration depth will not only directly affect the effective utilization rate of artificial reef,but also have a certain influence on the long-term stability of artificial reef.Exploring the influence law of different factors on the initial penetration depth of artificial reef can provide a theoretical basis for controlling the initial penetration depth in practical engineering,and controlling the initial penetration depth can effectively improve the stability of artificial reef.On the basis of sufficient data collection and literature review,this paper studies the initial penetration depth of artificial reef and the influence of initial penetration depth on stability.The main research work of this paper is divided into the following parts:(1)Carry out engineering geomechanical geotechnical tests of seabed soil in the study area.In-situ and laboratory geotechnical tests were carried out on the surface seabed soil of a Marine pasture in Shandong province,including in-situ shear strength test of micro-cross plate,direct shear test and triaxial consolidation without drainage test.(2)The whole process of artificial reef was analyzed and studied,and the mechanical response law of artificial reef in different stages was obtained.The mechanical model of artificial reef in water movement stage and the mechanical model of artificial reef penetrating into the seabed stage were established,and the numerical calculation of the two mechanical models was carried out by using MATLAB software.The influences of artificial reef weight,release height,opening ratio,structure,penetration Angle and seabed soil characteristics on the initial velocity and depth of penetration are analyzed.(3)The whole process of artificial reef was simulated by CEL method.Firstly,the underwater movement law of artificial fish reef is explored,and the change law of penetration velocity of artificial fish reef is analyzed,and the influence law of artificial fish reef weight,opening ratio and release height on penetration velocity of artificial fish reef is obtained.On this basis,the process of artificial reef penetrating into seabed is simulated numerically.The effects of artificial reef bottom shape,penetration Angle,penetration velocity and seabed soil quality on the initial penetration depth were investigated,and compared with the calculation results of mechanical model.The results show that the weight and opening ratio of artificial reef are directly proportional to the penetration velocity,while the release height is only proportional to the penetration velocity in a certain range.When the velocity reaches a critical value,the artificial reef will become uniform motion.The penetration Angle and penetration velocity of artificial reef are directly proportional to the initial penetration depth,and the shear strength of seabed is inversely proportional to the initial penetration depth.The shape of the bottom of artificial reef will affect the pressure distribution at the end,and the more uniform the pressure distribution,the smaller the initial penetration depth.The comparison shows that the numerical simulation results are in good agreement with the mechanical model calculation results,and the error is small,which verifies the correctness of the prediction model for the whole process of artificial reef placement in this paper.(4)The mechanical model and numerical model of artificial reef stability analysis were established by analyzing the stability of artificial reef at different penetration depths.The effect of penetration depth on the stability of artificial reef is studied.The results show that penetration depth is proportional to the maximum sea current speed that artificial reef can bear.The theoretical calculation method of stability considering the factors of penetration depth is put forward,and some reasonable suggestions are put forward for the engineering practice of artificial reef.