Specialized drilling and coring techniques and equipment have been developed by the Ocean Drilling Program (ODP) to recover fractured basalt cores in deep water. Cores were successfully retrieved in 5900 feet (1800 m) water depth using the new equipment during seatrials in June and July 1990. This paper presents the history of the development and use of the Diamond Coring System (DCS) equipment, and includes information on planned future enhancements to the system to improve operational efficiency.
TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractFatigue damage is an important consideration in the design of Tension Leg Platforms (TLP) foundations. The portion of fatigue damage from installation dominates the total damage of the pile foundation. Driving fatigue damage can be affected by factors such as soil resistance to driving (SRD) and hammer efficiency. A parametric study, utilizing data of Magnolia TLP to assess the effect that SRD and hammer efficiency had upon driving fatigue damage was performed.The results provided a database and guidelines for the field engineer to control the pile driving fatigue damage by adjusting hammer efficiency, if the field pile-driving blow counts were different from that predicted. The study proved to be important in reducing pile driving fatigue damage during pile installation.
Cores of granite and deformed sediment from the walls of Monterey Canyon were successfully recovered from December 30 to 31, 1992, by Monterey Bay Aquarium Research Institute's (MBARI) Remotely Operated Vehicle (ROV) Ventana using a small‐diameter, double‐barrel drill with a diamond bit. This HSTR (Holloway‐Stakes‐Tengdin‐Rajcula) drill was developed to drill cores horizontally from sulfide/sulfate walls of active black smokers. The drill was first successfully used by the submersible Alvin in October 1991 to drill into massive sulfide chimneys, on the Juan de Fuca Ridge (Eos, June 30, 1992, p. 273), and it was subsequently used with equal success on the chalcopyrite‐rich chimneys from 21°N and 9°N on the East Pacific Rise. The recent December dives, however, marked the first time that drilling has ever been attempted from the smaller ROV and the first time coring into the harder igneous rock substrate has been attempted.
Understanding the origin of the ocean crust by scientific drilling at the axes of mid‐ocean ridges is a high priority in the Earth science community, as reflected in the Ocean Drilling Program (ODP) Long Range Plan, the Joint Oceanographic Institutions for Deep Earth Sampling (JOIDES) Lithosphere Panel's White Paper, and several reports of the Ridge Inter‐Disciplinary Global Experiments (RIDGE) program. The ODP Long Range Plan provides for over a dozen drilling legs at and near mid‐ocean ridges prior to the year 2002, including a multileg drilling program at the East Pacific Rise (EPR). ODP Leg 142 (February–March 1992) was the first of this multi‐leg effort and was devoted primarily to continued testing and development of the engineering systems needed for successful drilling of bare rock at mid‐ocean ridges. At the same time, it was hoped that drilling would result in cores that could be used to study volcanic and hydrothermal processes, volcanic architecture, fluid flow, and other processes occurring at the active EPR axis.
The core barrel developed for use with the diamond coring system (DCS) was enhanced with several new components, along with three types of sediment sampling systems. A complete suite of fishing tools for recovery of both the inner barrel assemblies and outer core barrel was developed to complement the coring hardware. Primary hardware changes to the core barrel amounted to introducing a float valve into the outer core barrel and adding a basket-style core catcher to be run in tandem with the conventional collet-style catcher on the inner barrels. Extended crown bits were specifically designed for fractured and abrasive basalts expected at the East Pacific Rise (EPR) site for Ocean Drilling Program (ODP) Leg 142. In addition to the coring hardware, a DCS hydraulic piston sampler was designed for use with the existing DCS core barrel. Problems experienced with the secondary heave compensator on the DCS platform presented considerable difficulty in attempting to maintain constant weight on bit. While coring, the diamond bits were repeatedly impacted on the bottom of the borehole, causing catastrophic bit failure. In the course of attempting to correct the secondary heave compensator problems, some material was recovered that had been jammed into the inner barrel. No cores were actually cut with the DCS during Leg 142. This chapter describes the hardware additions to the DCS coring system and the deployment sequence necessary for operation of the hydraulic piston sampler. Discussion of the diamond bits that were run and suggestions for improvements to the system are also presented.
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