Available published data on the engineering properties of seafloor soils in the central northeast Pacific Ocean are synthesized and utilized in an analysis of the interaction of a tracked nodule harvester or dredge head with the seafloor. Bearing capacity, compressibility and trafficability of the soils are included in the analysis to the extent that available data will permit. Simple preliminary assessment of the feasibility of utilizing a tracked nodule harvester on the seafloor has emphasized both the need and the apparent dearth of good quality measurements of seafloor soil properties. Published information on lateral and vertical property variability is entirely too meager to be of significant value to any engineering analysis of the seafloor. The large capital investment and high risk associated with exploitation of manganese nodules requires increased knowledge of the engineering properties of deep-sea sediments. The expense associated with sampling and in situ testing dictates that the scientific and engineering communities cooperate fully to optimize both the quality and quantity of engineering data characterizing deep-sea soils.
Interest in pelagic or manganese nodules has resulted in a vast bibliography of papers reporting scientific results of studies made since the discovery of the nodules more than a century ago. The possibility of exploiting these nodules for their nickel, copper, cobalt, and manganese content has spurred scientific efforts to map and describe the origin of these deposits in recent years. Despite this spate of activity, remarkably little knowledge exists regarding the engineering properties of the deep-sea sediments in the principal nodule areas of the Pacific Ocean as well as in other oceans of the world. In November 1974. Deepsea Ventures, Inc. filed a notice of discovery and claim of exclusive mining rights and requested diplomatic protection and protection of investment with the U. S. Secretary of State. This mining claim was for the 60 Mm2 area bounded by latitude 140 16' to 150 44 1 N. and longitude 1240 20' to 1270 46' W. in a water depth of 2.3 to 5 km. Deepsea plans to commence commercial production by the end of 1989, by which time it appears likely that several other companies or consortia may also have begun to collect nodules from the northeast Pacific Ocean. It is general knowledge that many, if not most, commercial nodule harvestors or dredge heads will be in contact with the seafloor. Relevant information on the engineering properties of the sediments and how to use this information to design suitable dredge heads appears to be much less known. The purpose of this paper is to assess and synthesize briefly the meager existing geotechnical information for the northeast Pacific Ocean in an area approximately bounded by 1200 to 1500 W. longitude and the equator to 25 0 N. latitude; to discuss the design constraints of the nodule collector in light of existing geotechnical data; and to consider the implications of the inadequate geotechnical data, and what ought to be known before collectors are designed and harvesting operations begin at sea.
