Design Of An Automatic Marine Corer

Abstract

ABSTRACT Upon request of several geophysical organizations, a program was initiated at Texas A&M U. under the Sea Grant Program to design a self-contained automatic seafloor setting corer which willextract up to 50 ft of continuous undisturbed. core,operate in depths up to 1,000 ft of water,core in hard as well as soft material andbe as compact as possible to facilitate shipboard handling. This program was partially funded by Oceanonics, Inc., Houston, Tex. The SEACORE 50 will extract a 3-in. diameter core 49.5 ft long in 11 sections. The unit is octagonal in cross section measuring 6 ft side to side and is 12 ft in height. When the Unit reaches the seafloor, four legs fold down and level the unit on slopes of up to 15 °. The unit weighs 10,000 Ib dry, 8,000 Ib in water, and is lowered to the seafloor by a single power-tension cable. An automatic control system is continued in the unit with shipside manual control available at any time. A drill pipe fitted with a ring-type core bit is rotated under a considerable thrust load while water is pumped down the center of the drill pipe to wash the cuttings back up the annulus. This water is routed through the double-walled bottom joint around the core barrel so that the sample is not washed. A square rod extending from the top of the coring unit retains the rotation of the core barrel. This square rod also supports a piston in thecore barrel, thus affecting "fixed piston" coring. A hydraulic powerhead produces 1,000 ft-lb of torque and 6, 000 Ib of thrust or pull. INTRODUCTION The tools and techniques used today in ocean mining and exploration for obtaining undisturbed samples of the seafloor leave something to be desired. They require either logistic support from divers on the bottom or must be operated from a large surface ship with multipoint anchoring. Upon the request of several marine engineering concerns, a program was initiated at Texas A&M U. under the Sea Grant Program and partially funded by Oceanonics, Inc., Houston, to design a self-contained automatic seafloor setting coring device which will be capable of obtaining a 3-in. diameter core at least 50 ft long in depths of up to 1,000 ft of water. The recovered sample should be at least 90 percent of the amount drilled. The device should be activated with a power package on the ocean floor and supplied by a single umbilical cable from the surface vessel. It should be capable of rapid penetration and withdrawal to circumvent anchor spreads. It should be as compact as possible to facilitate ease of shipboard handling. The device should employ both rotary and push-type operations with interchangeable coring bits to handle all types of sediments and must employ the fixed-piston.