Large Deformation Numerical Simulation Of Plate Anchor Keying

Suction embedded plate anchor is a mooring system for mooring large offshore floating production devices on the seabed.It has the advantages of accurate positioning,high efficiency and economy.It has been used more and more in deeper sea areas.Suction embedded plate anchor will cause a certain loss of buried depth in the process of large deformation rotation.In this paper,numerical simulation is used to study the bearing capacity and deformation mechanism of anchor chain and plate anchor in the process of rotating resistance of plate anchor.Firstly,the large deformation cutting motion of anchor chain in soil is simulated.The interaction between chain and soil provides a part of the pullout bearing capacity for plate anchor.Considering the non-backflow characteristics of the soil when the anchor chain cut through the soil and the cavity formed during the movement of the soil,the profile of the anchor chain in the soil during the anchoring process is studied.The results show that the anchor chain forms an inverse catenary shape in the soil with the interaction of chains and soil,and the horizontal distance between the padeye and the anchor chain at the mud line increases with the increase of the mud line load.In the process of force transferred along the anchor chain direction,the difference between backflow and non-backflow decreases with the increase of normalized chain tension at mud line.At a certain depth,with the increase of anchor chain tension at mud line,the influence of cavity depth on chain profile in soil decreases gradually.Then,the bearing mechanism of large deformation rotation of plate anchor in homogeneous soil is analyzed.The CEL(coupled Euler-Lagrange method)in ABAQUS is used to simulate the interaction between anchor chain and soil.The large deformation envelope equation of plate anchor is coupled.The tension and inclination at the padeye of the plate anchor are acted on the bottom of anchor chain through VDLOAD user subroutine.The numerical simulation of large deformation rotation of plate anchor driven by pull chain is realized.The change of bearing capacity of plate anchor with different inclination at mud line chain is studied.When the plastic limit theory is satisfied,the change of the inclination of plate anchor and the relationship between embedment loss and bearing capacity are analyzed.Through the analysis of different inclination of anchor chain at the mud line,it can be concluded that the greater the inclination of anchor chain at the mud line,the greater the embedment loss of the plate anchor.The results show that the embedment loss of the plate anchor decreases with the increase of normal eccentricity.When the plate anchor is retracted from the right side of the anchor,the anchor will rotate counter-clockwise,then turn clockwise and pull up with the small inclination of anchor chain at the mud line.Finally,numerical analysis is carried out for the rotational uplift of plate anchor in heterogeneous soil.According to the characteristics of seabed clay,user subroutines VUSDFLD and VUFIELD are used to analyze the bearing mechanism of plate anchor with large deformation and rotation under the condition of soil strength varying with depth.Provide theoretical support for site construction.By comparing homogeneous soil with heterogeneous soil,it is found that under the same conditions,the embedment loss of plate anchor in heterogeneous soil is greater than that in homogeneous soil.