Simulation Analysis Of Penetration Process Of Torpedo Anchor

Today there are many countries in the world set their sights on the ocean, so a secure and stable basement of mooring system is very important for large deepwater oil and gas prospecting. Torpedo anchor is one new style of basement with high capacity. It has been verified that it owns enough safety performance for FPSO and so on. This paper reports the model simulation of two installation processes including the accelerate process in water and penetration process in soil.According to the resistance analysis, this paper gives the mathematical model of the process in water. In order to get the relationship between the release height and the initial penetration velocity, this process is simulated by Matlab software with numerical theory and by Abaqus software with CEL theory. Then the objective law of movement in water is summarized by compare the two results.The second process is penetration in the seabed, the torpedo anchor will overcome the anchor bottom pressure and the lateral friction resistance and move into the seabed. The penetration process is divided into three stages for the first time in this paper:the immersion stage, the stable penetration, the stopping stage. By analysis the changes of soil element pressure and the trend of velocity, the cause of these phenomena was summarized. What’s more, the separation phenomenon happened in third stage was found which caused the velocity disorder.Initial penetration depth is effected by the property of seabed soil such as density, cohesion, internal friction angle and so on. The anchor is released to penetrate in three different soil material in parameters, then explore the relationship between them. The bottom shape parameters of anchor will affect the distribution of pressure and it is easier for clipper-built shape to penetrate in the seabed when compared with other shape. Adding its weight for anchor is a effective way to increase penetration depth, but it will also bring some bad effect that is a bigger frictional resistance caused by a bigger superficial area. So it is important to select a proper weight. When come to the initial penetration velocity in the installation process, accuracy should also be considered.Torpedo anchor and chain will get many resistance such as ocean current and rock impact and then the direction of motion will tilt. So directional stability is a key property for anchor in order to get a right attitude before penetration, this issue has been simulated in this paper.