It is expected that some of the deep-sea sediments will be lifted along with water and manganese nodules by a hydraulic transportation system, and either be discharged near the seafloor or at the surface. This discharge may create a turbid sediment plume, changing the physicochemical conditions of the surrounding waters, and affecting the ecosystem in the area. The volume and effect of discharged sediments has been worked out in some of the earlier studies; During the hydraulic transportation and before the discharge, the sediment particles may breakup and undergo morphological alteration, due to attrition with one another as well as the inner surface of the pipe and the lifting system. However, the effects of transportation on sediment particles have not been examined as yet. This paper is an attempt to study the initial effects of movement of sediment particles in a labordtory assembly, consisting of a set of pipes and a pump. The results are expected to be useful in planning similar tests on a larger scale, as well as in understanding the nature of sediment particles at the time of discharge from a deep-se-d mining system.
Deep-sea manganese nodules are being considered as potential alternative sources for strategic metals, such as Mn, Cu, Ni, and Co, for the future, due to their vast distribution and relatively higher metal concentration (Mero, 1965), Several registered Pioneer Investors have already identified promising sites of manganese nodules in the deep-sea regions (ISA, 1998) in the Pacific and Indian Oceans. Following the large scale ocean mining tests by international consortia about twenty years ago (Welling, 1981; Kaufinan et aI., 1985; Bath, 1989; Shaw, 1993),. several national R&D projects have been initiated for development of deep-sea mining systems (Herrouin et aI., 1989; Inokuma, 1995; Yang and Wang, 1997; Muthunayagam and Das, 1999).
