Abstract
Among the deep ocean manganese nodule mining technologies, the sea floor collector design is the most complicated and insoluble one. Manganese nodules are distributed on the surface of the vast and low strength pelagic sediments, which compose mainly of biogenic siliceous material and clay minerals. The sea floor collector will be supported by the deep ocean sediment layer and travel on it with steering to avoid obstacles. It will pick up and collect manganese nodules from the sea floor and reject undesirable materials such as sediment and oversize objects. Geotechnical properties of the deep ocean sediment layer play a very important role in the design of the sea floor collector.
Several important physical and geotechnical properties, such as water content, particle size, consistency, vane shear strength, sensitivity, uni-axial compressive strength, and tri-axial strength, of the Pacific deep ocean sediment layer were measured on board and in laboratory on land using box core samples collected from the ocean floor where the manganese nodules distribute. Then, its dynamic geotechnical properties were measured by newly proposed method in which a fallen collider was applied onto the test-specimen surface and they were compared with the static properties. It is concluded that the vane shear strength can be a representative indicator of the geotechnical properties of the deep ocean sediment layer for the collector conceptual design.
