南極ドームふじ深層掘削孔の検層における液温測定値の評価と補正

第6回極域科学シンポジウム[OM] 極域気水圏11月16日（月）　国立極地研究所１階交流アトリウ

Improvement of drill system for the third deep ice coring project around Dome Fuji, Antarctica - Focusing on selection of drilling fluids -

The Tenth Symposium on Polar Science/Ordinary sessions: [OM] Polar Meteorology and Glaciology, Wed. 4 Dec. / Entrance Hall (1st floor) , National Institute of Polar Researc

Borehole measurement of deep ice coring site at Dome Fuji, Antarctica and characteristics of basal ice near bedrock

第2回極域科学シンポジウム　氷床コアセッション 11月16日（水） 国立極地研究所 2階大会議室前フロ

An experiment on ice cutting under high liquid pressure and 1ow temperature

In order to examine dependencies of hydro-pressure and ice temperature in ice cutting performance of a drill for deep ice coring, experiments on ice cutting were carried out under liquid pressure from 0.1MPa to 30MPa at temperatures of 12.3,-40.3℃ and -62.0℃ changing the rake angle of the ice cutter. The results showed the penetration speed of the drill for a given rake angle decreased for at lower temperature and higher pressure; for a constant penetration speed, larger torque was required at higher pressure and lower temperature. Also, the larger the rake angle, the smaller the penetration speed. When the rake angle of the ice cutter was 17°, the drill performed at the designed penetration speed

Borehole logging device at Dome F, Antarctica

A borehole logging device is newly developed for deep drilling to start from 1995 at Dome F, Antarctica. The device is designed to measure the diameter, inclination and azimuth of a hole, ice temperature and fluid pressure. A logging sonde, 2.35m in length and 114mm in diameter, has two sets of stabilizers and a caliper with three contact points. The possible range of measurement is from 130 to 170mm in hole diameter. The data are transmitted by a microprocessor mounted in the sonde to a personal computer at the ice sheet surface

Ice core drilling on Southern Patagonia Icefield -Development of a new portable drill and the field expedition in 1999-

A 45.97m-deep drilling operation was carried out during November/December 1999 on the accumulation area of Tyndall glacier (50°59′05″S, 73°31′12″W, 1756m a. s. l.) at the southern end of the Southern Patagonia Icefield. A portable electromechanical drilling system was developed for ice-coring on temperate glaciers which often have aquifers near the pore-close off depths. The firn-core obtained was subjected to visual stratigraphic observations and bulk-density measurements. Preliminary results suggest an extremely high accumulation rate (about 12-14m a^ w. e.) at the drilling site. The drilling operation was strenuous because of the continuous strong wind and enormous snowfall which forced the members to survive for nearly three weeks in a snow cave before evacuation

Development of a JARE deep ice core drill system

The final design of an electro-mechanical drill is very simple both in shape and in mechanism. It is a straight tube consisting of an antitorque section, motor and computer section, chip chamber and core barrel. Three cutters (rake angle : 30 to 40 degrees, pitch : 5 to 7mm) are attached to cut an ice core 94mm in diameter and bore hole 135mm in diameter. The maximum core length is 2.1m long. Chips are transported between the core barrel and the outer tube by spiral rim attached to the core barrel. No motor for sucking chips up to the chip chamber is installed. The chips are separated from liquid by the filter at top of the chip chamber, and are compacted to the density of 500kg/m^3. In the pressure tight electronics section, a computer, DC brushless motor (270V, 600W, 12000rpm) and reduction gear (1/170) are installed. The antitorque section has three leaf springs. A steel cable 7.7mm in diameter has been chosen. The actual drilling operation is easy, for in response to the cutter load, a switching signal (go or stop) can be sent from the relay computer to the winch controller. What an operator has to do is, before drilling, to set the winch speed at the proper value and set the threshold value of the cutter load, and, while drilling, check the motor current if it increases rapidly