Overview of Physical Characteristics of Deep-sea Polymetallic Nodules and the Effects on Mining and Transportation Processes

Abstract

This study aimed at determining the physical characteristics of deep-sea polymetallic nodules and analyzing their influence on the mining and transportation process, so as to guide engineering applications. This work summarized the latest progress of deep-sea mining of polymetallic nodules, through the statistics and regression analysis of available data, the formation mechanism of polymetallic nodules and the main composition, the distribution characteristics on the sea floor, the morphology and structure, the relationship between size and weight, water content, density, pore characteristics, the strength and other key physical properties were determined. The study indicated that the polymetallic nodules were of various shapes, and it was loose and porous, the water content was high, and they were approximately uniformly distributed on the seabed or in shallow mud. The joint probability distribution of particle mass and size had a long right tail, more generalized joint probability density function of copula should be used in accurately modeling. Besides, the tensile strength of nodule decreased logarithmically with the increase of nodule diameter. In addition, the mining of nodules in deep-sea high-pressure environment required more energy consumption, and the nodules exhibited higher ductility. Combined with the theory of solid-liquid two-phase flow analysis and particle settlement theory, the influence of main parameters such as shape, size and density of nodules on the hydraulic lifting process was analyzed, the main way and law of particle fragmentation were determined, and the possible causes of blockage caused by transportation with different particle sizes were summarized.

Keywords

• polymetallic nodules
• morphology
• density
• porosity
• strength
• hydraulic lifting
• fragmentation