The shallow drill
Compared to the hand auger, the shallow drill system is much larger, heavier, and more complex. The complete standard setup, when deployed with tools, spares and a power generator, weighs in at 800 kg, 10 times the weight of the hand auger. The shallow drill can be placed on 2 Nansen sledges to be towed with a ski-doo or can be carried by a small plane (e.g. a Twin Otter) to less accessible drill locations.
Similar to the hand auger, the shallow drill collects 74 mm diameter core, starting from 2 m below the surface and descending down to a maximum of 350 m. This drill system is an electro-mechanical drill lowered and raised by an electrical winch with a tilting tower on the surface to ease handling the drill and extracting the core.
The core barrel and drill head are similar to that of the hand auger in most respects, but the core barrel is contained inside a second outer core barrel which does not rotate during drilling. Thick spirals on the outside of the core barrel and vertical grooves on the inside of the outer core barrel help transport the drilled ice chippings to the top of the core barrel where they are contained in a plastic insert on top of the core. The core segments drilled are about 1 meter long.
The drill, from top to bottom, consists of
- An anti-torque section to provide the drill with a firm grip of the borehole walls preventing the drill outer and upper sections from spinning when the drill head is rotating.
- A motor section with 160 V DC motor to rotate the drill head and inner core barrel.
- A long outer core barrel containing the inner core barrel and the chip chamber.
- A drill head to cut into the firn and ice (not visible in the picture).
Preparation to start drilling takes approximately 3 hours, involving
- Assembly of tower and drill.
- Digging of an inclined trench into which the tower tilts.
- Levelling of tower.
- Setting up drill and winch controller.
- Setting up of core logging area.
- Setting up of the power generator.
The drill is normally operated by one person while a second person logs and packs the core. A two person team can extract around 50 m of core a day under optimal conditions.
Ice Core Drilling Projects