A portable drilling rig for goring permafrosted sediments

We describe a portable drilling system that uses compressed air for caring permafrosted glacigenic sediments to depths of 10 meters. Standard HQ and N Q diameter core barrels, bits, and drill rods were used with a purpose-buil t, portable compressor, which could produce 50 cubic feet (1.4 m(3)) of air per minute at 30 psi (200 kPa). The drill string was rotated by a Stihl 05 6 motor mounted on a frame and hung from a hand winch on a tripod. The supp ly of compressed air is critical to keep the drill bit at subzero temperatu res and prevent melting of the core and nearly instantaneous freeze-up of t he drill string should rotation unexpectedly stop. Cooling the bit depends on the temperature and volume of air entering the hole as well as the kerf and diameter of the bit. Diamond bits are best for coring igneous clasts, b ut tungsten bits are best for coring ire lenses and soft friable sands. Goa d core recovery of unconsolidated sands and gravels is possible only if the y are firmly frozen in place.