Continuous Bucket-Line Dredging at 12,000 Feet

Abstract

ABSTRACT Testing of a continuous bucket-line dredging system was carried out in the South Pacific August 23 through September 14, 1970 by Japan Resources Association aboard the vessel "Chiyoda Maru No. 2". Fifteen dredge stations were occupied, and the system was tested at depths of 1080, 3755, and 1220 meters. The system is designed to recover manganese nodules, and the tests helped to verify its feasibility. A brief discussion of the merits of the continuous. bucket-line compared to other continuous systems is made. INTRODUCTION On 23 August 1970, the vessel Chiyoda Maru No.2, under charter to the Japan Ocean Resources Association, left Papeete in Tahiti on the first leg of a three-week test and survey cruise, in the vicinity of the Tuamotu Archipelago. The objectives of the cruise were to test a large-scale model continuous bucket-line dredge under field conditions in water depths of more than 1,000 meters and to procure for test purposes a quantity of high-cobalt, ferromanganese nodules. Additional areas of high-cobalt nodules in the South Pacific were to be sampled and surveyed. This paper describes the work leading to the successful testing of the dredging system at a depth of 3,755 meters. History and Background The Japan Ocean Resources Association (JORA), which operates a joint cooperative program between government and industry, was formed in 1967 to further the concepts of the senior author on the application of a continuous bucket line system to the dredging of manganese nodules in the deep ocean. Laboratory and field tests of the system on a small scale were carried out successfully in 1967 and 1968, on the latter date in maximum water depths of 1,410 meters. In July of 1969, a one-ton sample of nodules was retrieved for test purposes from an area southwest of Baja California with a simple drag bucket line deployed from the chartered vessel "Oceaneer". Tests on a larger-scale continuous system were then planned and funded, resulting in the Second Survey Cruise and Mining Test described here. Table 1 lists the test series carried out to date. Principal of the Continuous Bucket-Line Dredge When a bucket at the end of a rope is dragged over the ground, it scoops up soil and other loose material. The rope may then be used to lift the bucket and its contents to a place where the contained material may be dumped. This is the principal of the dragline, a very simple and effective tool, used widely for the excavation and mining of earth materials.