Light-weight coring in permafrost at GSC - current activities

Abstract

Light-weight coring techniques used by the GSC in recent years include coring with a modified Cold Regions Research and Engineering Laboratory (CRREL) barrel and a diamond impregnated bit barrel. The modified CRREL barrel is a hollow mild steel barrel with welded double helix flight configuration. The removable shoe has replaceable tungsten carbide teeth which do the cutting. Attached to a power head, the CRREL barrel can retrieve a high-quality, continuous core in snow, ice, and fine-grained organic and mineral soils. The disadvantage of the CRREL barrel is that is does not work well in stony ground, unfrozen soils or soils with a significant unfrozen water content. In addition, the drilling process can be slow due to insufficient storage for the cuttings on the outside of the barrel limiting the length of core recoverable in a single run. A second method used by the GSC is diamond drilling, which uses a core barrel with a diamond impregnated carbide bit. Also attached to a power head, this method can cut through fine-grained soil with ice, sand, gravel, and boulders up to 20 cm in diameter. This off the shelf equipment produces a high quality continuous core. The disadvantages are that in pure ice the core tends to break into smaller segments, slowing drilling, and in warmer permafrost conditions (-2 to 0ºC) the core tends to disintegrate due to the uncemented material and frictional heat. Both methods are applicable in a wide range of terrain types, they are light-weight and easily transportable by snow machine, ATV trailer and helicopter.