The XCB system is a rotary system with a small cutting shoe that extends below the large rotary APC/XCB bit (Figure F3). The XCB system is used to advance the hole when HLAPC refusal occurs before the target depth is reached or when drilling conditions require it. The XCB system can also be used to either initiate holes where the seafloor is not suitable for APC coring or be interchanged with the APC/HLAPC system when dictated by changing formation conditions.
The XCB system is typically used when the APC/HLAPC system has difficulty penetrating the formation and/or damages the core liner or core. Use of the HLAPC system allowed for significantly greater APC sampling depths to be attained than would have otherwise been possible. During use of the HLAPC system, the same criteria are applied in terms of refusal as for the APC system. In most instances, the HLAPC system is deployed after the standard APC system has repeated partial strokes and/or the core liners are damaged. The standard APC system uses a 9.5 m long core barrel, whereas the HLAPC system uses a 4.7 m long core barrel.
When a full or partial stroke is achieved but excessive force is not able to retrieve the barrel, the core barrel can be "drilled over," meaning that after the inner core barrel is successfully shot into the formation, the drill bit is advanced to total depth to free the APC barrel. When a full stroke is not achieved, one or more additional attempts are typically made, and each time the bit is advanced by the length of the core recovered (note that for these cores, this results in a nominal recovery of ~100%). For APC cores that do not achieve a full stroke, the next core can be taken after advancing to a depth determined by the recovery of the previous core (advance by recovery) or to the depth of a full APC core (typically 9.5 m). The driller can detect a successful cut, or "full stroke," by observing the pressure gauge on the rig floor because the excess pressure accumulated prior to the stroke drops rapidly.ĪPC refusal is conventionally defined in one of two ways: (1) the piston fails to achieve a complete stroke (as determined from the pump pressure and recovery reading) because the formation is too hard, or (2) excessive force (>60,000 lb) is required to pull the core barrel out of the formation. The inner barrel then advances into the formation and cuts the core (Figure F2). After the APC/HLAPC core barrel is lowered through the drill pipe and lands above the bit, the drill pipe is pressured up until the two shear pins that hold the inner barrel attached to the outer barrel fail.
The APC and HLAPC systems cut soft-sediment cores with minimal coring disturbance relative to other IODP coring systems. The final hole position was the mean position calculated from the GPS data collected over a significant portion of the time during which the hole was occupied. Dynamic positioning control of the vessel primarily used navigational input from the GPS (Figure F1) we deployed a seafloor beacon only at Site U1536, which was the deepest penetration site, during this expedition. Once the vessel was positioned at a site, the thrusters were lowered and a seafloor positioning beacon was prepared for deployment in case it was needed. A SyQwest Bathy 2010 CHIRP subbottom profiler was used to monitor seafloor depth during the approach to each site and to confirm the seafloor depth once on site. GPS coordinates (WGS84 datum) from precruise site surveys were used to position the vessel at Expedition 382 sites. Methods used by investigators for shore-based analyses of Expedition 382 data will be described in separate individual postcruise research publications. This information applies only to shipboard work described in the Expedition reports section of the Expedition 382 Proceedings of the International Ocean Discovery Program volume. This section provides an overview of operations, depth conventions, core handling, curatorial procedures, and analyses performed on the R/V JOIDES Resolution during International Ocean Discovery Program (IODP) Expedition 382. Keywords: International Ocean Discovery Program, IODP, JOIDES Resolution, Expedition 382, Iceberg Alley and Subantarctic Ice and Ocean Dynamics, Site U1534, Site U1535, Site U1536, Site U1537, Site U1538, Subantarctic Front, Pirie Basin, Dove Basin