Abstract: Deep ocean mining pipe has large deflective dis- placements because of ocean currents and the drawing of the mining vessel, which is a geometric nonlinear problem. The lifting pipe is simplified as nonlinear beam elements, the finite element modeling is built by menas of T. L. method, the rigid matrix is deduced by means of energy method, and the calculating method of hydrodynamic force and the Newton-Raphson iterative method in incremental step are presented. The effects of the different drawing velocities of the mining vessel, the weight of the buffer and joining methods between the pipe and the vessel on deflective displacements of the lifting pipe are analyzed. Calculating results show that drawing velocities of the mining vessel and the weight of the buffer have a great influence on deflective displacements of the lifting pipe, while the joining methods between the pipe and the vessel have little influence on deflective displacements. A theoretical analytical method and a designing basis for the reasonable design of the deep ocean mining system are provided.

Key words: Deep ocean mining, Hydrodynamic force, Lifting pipe, Nonlinear finite element method