The ocean mining pipe connects the sea floor to the mining ship and remains suspended in hostile sea environment carrying nodule slurry. This pipe shows nonlinear behavior due to large deflection under hydrodynamic forces, due to waves, current, ship velocity, and ship-induced vibration. A finite element formulation has been developed for the two dimensional nonlinear coupled response of the pipe system categorized as system -I and system -II. Pipe top is pinned to the ship and the bottom end is connected to the nodule collector/equipment in system-I. In system -II bottom end is kept free of the self-propelled seafloor nodule miner and top end is connected to the ship. The mineral ore is transported from the sea bed to the mining ship in the form of slurry. Primarily the study aims at the determination of dynamic characteristics of the mining pipe considering different boundary conditions. Instantaneous geometric nonlinearity has been taken into consideration through inclusion of geometric stiffness matrix. The added mass effect has also been taken into account together with the self weight of the pipe. A direct step by step integration in the time domain has been adopted to solve the equation of motion. An iterative scheme utilizing the normal mode theory has been employed to decouple and solve the equation of motion. Results show the significance of dynamic characteristics, bending moment distribution and deflected profile of the pipe in a varied marine environment.
Ocean mining is a challenging area both for field and research engineers. Underwater mining pipe is an efficient means of mineral transportation from the, ocean bed to the sea surface. A reliable pipe system for such a complex operation demands a realistic and detailed dynamic analysis. Deep ocean mining is gaining impetus worldwide.