Dynamic Analysis Method Of Embedded Large Cylindrical Structure Considering Cumulation Of Plastic Deformation Of Soft Soil Under Cyclic Loads

The large diameter cylinder structure is a new type of preferable structure in the soft soil and deep water to build breakwater. The states of subsisting and the destructive forms of the large diameter cylinder breakwater have the obvious dynamic characters under the wave impact. But the working mechanism and the reasons of destruction are still not entirely clear. One important reason of destruction is the cumulation of plastic deformation of soft soil under cyclic loads.Accordingly, the primary purpose of this paper is to research the dynamic properties of the large diameter cylinder structure under the wave impact, and the cumulation of plastic deformation of soft soil under cyclic loads in this kind of structure. This paper also analyses the factors of dynamic stabilities of the large diameter cylinder breakwater structure.This paper combines the advantages of the simplified method of the large diameter cylinder breakwater and the FEM, founds a dynamic calculation system model. This model takes the large diameter cylinder as a discrete rigid body system, and takes the ground as a discrete tri-dimension nonlinear spring-damp system. The parameters of the model are confirmed by employing the modified model of combining equivalent linear model and D-P yield criterion. The paper brings that the spring stiffness of the soil-spring is equal to zero or a very small value when it reaches yield state, and then take a unvaried force to this yield point.This paper brings the method of calculating the cumulation of plastic deformation of soft soil under cyclic loads in the large diameter cylinder breakwater structure. The results prove that this method is feasible. The paper also analyses the influence factors of the cumulation of plastic deformation which include the criterion of starting time of the cumulation, the dimension of the large diameter cylinder, the depth of cylinder, the parameters of soil and the exterior loads.