A discrete element method (DEM) is proposed for the analysis of deepocean mining pipe system based on the combination of multi-body dynamics and structural dynamics. The pipe is divided into some rigid elements that are linked by flexible connectors, which are described by 6-DOF stiffness coefficients. First two examples are given to show that the DEM model is feasible. Then the three-dimensional DEM model is used to perform dynamic analysis of the entire deep-ocean mining pipe system, including lift pipe, buffer and flexible hose. The top of the lift pipe is hinged at the ship, and the bottom of the flexible hose is connected to a self-propelled seafloor miner. The dynamic motions of the entire mining pipe system under different work conditions are discussed.
Typical deep-ocean mining system is composed of ship, lift pipe, buffer, flexible hose and miner. The dynamic analysis for the mining system, including every subsystem behavior and combined behavior of entire system, can provide theoretical explanation and technical reference for the design and operation of mining system. Especially, the dynamic behavior of pipe system is one of the most crucial problems for the entire mining system. Various analyses and studies have been carried out about the pipe system, which connects the seafloor miner to the ship. Since 1980 Chung et al.(1981) have done a great deal of work about long vertical pipe by finite element method, for example, a nonlinear finite element code was developed to model 3-D dynamic behavior of long vertical pipe by Chung and Cheng (1994). Grebe and Schwarz (1996) have calculated the flexible hose behavior with lumped mass-spring model, in which each point mass possesses three displacements in the three co-ordinates directions and the effects of the bending behavior can't be described.
