Document DetailsISTUK: A deep ice core drill system
|Authors:||Gundestrup NS, Johnsen SJ and Reeh N|
|Periodical/Journal:||Proceedings of the Second International Workshop/Symposium on Ice Drilling Technology (eds G. Holdsworth, K.C. Kuivinen and J.H. Rand), CRREL Special Report 84-34|
The ice core drill system used to core to bedrock at a depth of 2037.63 m near Dye-3 in South Greenland (65° 11'N 43° 49'W h = 2490 m) is described. The drill is designed to provide good core quality and to be easy to maintain in the field. It is a probe type system, with the drill suspended on a 6.4 mm cable. The drill consists of two parts. An antitorque section prevents rotation of the upper part, containing the motors and the electronics. During drilling, the ice chips, produced by the ice cutters, are sucked into the lower, rotating part of the drill. The chips are transported inside the drill to the surface, where the drill is camped to a 6 m tower and tilted to a horizontal position for easy core removal and drill cleaning. The cutters work like a plane, which reduces the cutting power and provides stable penetration, essentially independent of the load on the cutters. the drill is powered by a rechargeable battery pack, and is controlled by a microprocessor in the drill. The length and weight of the drill are 11.5 m and 180 kg, respectively. The tower and the winch including an electro-hydraulic pump station and 2500 m of cable weigh 900 kg total. Core length is about 2.2 m per run, and the weekly production is 120 m of 10 cm diameter core at 2000 m depth. The core recovery is better than 99.9 percent. Close to bedrock the hole deviates 6 deg from the vertical, and the temperature is -13 degrees C (-20 degrees C at surface). The hole is filled with a mixture of JET A-1 and PCE. The liquid is cleaned by a down borehole filter unit. The hoe diameter is maintained with a reamer.