Studies on the Safety and Control of the Deep Ocean Mining System

从深海海底开采矿产资源，需要一根管柱将海面上的采矿船与海底的收集器或采矿机连接起来。此外，在矿石的泵举系统中，管柱必须配备一个或多个泵模块，用于将矿产资源泵送到船上，并配备缓冲装置，以调节管柱中矿液混合物的密度，并发挥重量的作用，以稳定管柱的力学行为。由于船舶运动，该系统中的管柱容易产生纵向和横向振动。因此，为了上述采矿系统的安全运行，必须控制管柱的这些振动。在1990财年，建立了作用在泵模块和缓冲器上的流体力的评估方法，并利用该方法确定了作用在不同形状的泵模块和缓冲器上的流体力。然后，对管柱纵向振动和横向振动进行了分析，发现就管柱强度而言，纵向振动比横向振动更具破坏性。在1991会计年度，研究了泵模组和缓冲器对管柱纵向振动的形状效应，结果表明，产生较大阻力的泵模组或缓冲器对降低管柱纵向振动更有效。因此，具有最佳形状的缓冲器可使管柱振动的共振幅值降低约40%。接下来，为了同样的目的，在泵模块和缓冲器上附加了减振器。然后，发现附着在缓冲器上的减振器可以使管柱的共振幅值降低50-63%，管柱产生的最大轴向应力降低18-40%。并确定了减振器的最佳设计条件。

For mining mineral resources from deep sea bottoms, a pipe string is needed to connect the mining ship on the sea surface with the collector or miner on the sea floor. Furthermore, in the pump lift system of ore, the string must be equipped with one or more pump modules for pumping the mineral resources up to the ship and with the buffer which regulates the density of ore-fluid mixture in the pipe string and plays a role of the weight to stabilize the mechanical behavior of the string. The pipe string in this system is apt to vibrate longitudinally and laterally due to the ship motions. Hence, these vibrations of the string must be controlled for the safe operation of the above mentioned mining system.In the fiscal year of 1990, the method evaluating fluid forces acting on the pump-modules and, the buffer was established, and the fluid forces acting on various shapes of the pump-modules as well as buffer were determined by this method. Then, the longitudinal and lateral vibrations of the pipe-string were analyzed, and the former was found to be more destructive than the latter as far as the strength of the pipe-string was concerned.In the fiscal year of 1991, the shape-effects of the pump-modules and buffer on the longitudinal vibration of the pipe-string were examined, and the pump-modules or buffer causing higher drag force proved to be more effective in order to reduce the longitudinal vibration. Thus, the buffer with the optimum shape for this purpose could reduce the resonance amplitude of the vibration of the pipe-string by about 40%. Next, vibration absorbers were attached to the pump-modules as well as the buffer for the same purpose. Then, i t was found that the absorber attached to the buffer could reduce the resonance amplitude of the pipe-string by 50-63% and the maximum axial stress produced in the pipe-string by 18-40%. Moreover, the optimum condition for designing the vibration absorber was determined.