Soil mechanical pickup device Interaction in deep sea bed Polymetallic nodule mining by Laboratory investigations

Abstract

Mineral resources from the oceans will augment land-based minerals in meeting future demands of mankind. Deep-sea exploration has revealed huge deposits of mineral resources in various forms such as manganese nodules, cobalt-rich manganese crusts and polymetallic massive sulphides in numerous locations at depth ranging from 4,500 to 6,000 m in different oceans and seas. Amongst them polymetallic nodules, which are available on the sea floor loosely in the sediments are the easiest to extract. Technology is being developed by various countries to recover them remotely from surface ships, with least environmental risks to marine eco-system. The National Institute of Ocean Technology (NIOT) in India is conducting research to develop, deep sea bed polymetallic nodules mining technology in line with the International Sea bed Authority s (ISA) policy. As part of it, a self-propelled tine type mechanical mining machine was developed to pick up nodules by combing action. In the current research, the performance of the above-mentioned mining equipment was evaluated in the Soil-Machine Interaction Laboratory in a 14 m long specially constructed state of the art simulation tank, which has numerous amenities including a soft cohesive bentonite soil bed, which simulates deep sea bed. The experiments were carried with 2.5 kg/m2 of nodules abundance and 1.5 (± 0.2) kPa shear strength of soil bed by varying the operating parameters, namely haulage speed, digging depth and pickup device angle of inclination. A custom-designed bentonite soil mixing machine was designed, developed and used to mix and level the soil to maintain uniformity in the shear strength of the soil bed throughout the tank and also to haul the wheeled carriage on which the nodule pickup and other devices were iv mounted. The experiments were conducted using artificial and polymetallic nodules. No-load tests were performed by varying the haulage speed from 0.0375 to 0.3 m/s. Load tests were conducted by varying the independent input operating parameters namely