Ice Specimen Retrieval and Coring Method for Accreted Ice on Vertical Piles Subjected to Tidal Changes

Abstract

Ice-coring auger machines can cost thousands of dollars and are generally made for vertical extraction from sea ice or glaciers. This project required specimens from ice accreted onto vertical piles at the Port of Alaska (POA) in Anchorage, Alaska, which meant the extraction was horizontal and had to be completed during the short low-tide window. In this paper, we describe the development of a method for economically harvesting and processing the accreted ice from the POA into cylindrical cores and shear beams. The ice was harvested by cutting large cubes out of the in situ mass with a chainsaw and then lifting these onto the port deck using a crane. The cubes were then transported to a laboratory walk-in freezer to be processed. Ice cores were drilled from the cubes using a custom-fabricated core bit made from metal tubing and hole saws. This simple core bit quickly produced smooth ice surfaces, provided there was a mechanism for evacuating the cut ice chips during drilling. To facilitate this, an alignment template was used to locate and drill two adjoining evacuation holes prior to coring. These evacuation holes had to be precisely located to be adjacent, parallel, and connected with the outside diameter of the forthcoming core, but were not allowed to impinge on the core. With this new method, an ice block can be converted into up to a dozen test-ready compression ice cores within a few hours. The variability in the diameter of the ice cores was found to be small, with a coefficient of variation of < 0.4%.