Item: The effects of soluble impurities on the mechanical behaviour of polycrystalline ice
-
-
Title: The effects of soluble impurities on the mechanical behaviour of polycrystalline ice
Proceedings: International Snow Science Workshop Proceedings 2018, Innsbruck, Austria
Authors:
- Kevin Hammonds [ Montana State University, Dept. of Civil Engineering, Bozeman, MT, USA ] [ Dartmouth College, Thayer School of Engineering, Hanover, NH, USA ]
- Ian Baker [ Dartmouth College, Thayer School of Engineering, Hanover, NH, USA ]
Date: 2018-10-07
Abstract: The Earth’s ice sheets, glaciers, and snowpacks contain a wide variety of naturally occurring impurities, both soluble and insoluble, including dust, black-carbon, sulfuric acid, nitric acid, and even some living microbial organisms. Understanding how these impurities affect the intrinsic mechanical and thermodynamic properties of ice and snow, however, is not well understood. To investigate the effects that only trace amounts of H2SO4 (sulfuric acid) and CaSO4 (gypsum) have on the mechanical behavior of polycrystalline ice, a series of mechanical tests were conducted at temperatures between -6 and -20°C using H2SO4- and CaSO4-doped laboratory-prepared specimens of polycrystalline ice. Parallel tests were also performed on identical but undoped specimens of polycrystalline ice. Mechanical testing included constant-load tensile creep tests and compression tests at constant displacement rates. Postmortem microstructural analyses were performed using cross-polarized light thin section imaging, Xray computed microtomography, Raman spectroscopy, and scanning electron microscopy. It was found that the structural integrity of the H2SO4-doped specimens of ice was reduced, when compared to the undoped ice, while the CaSO4-doped specimens of ice was increased. Additionally, H2SO4-doped specimens also exhibited an earlier onset of microcracking at lower strain rates than the undoped ice and were found to have larger grain sizes at strains greater than 5%. Furthermore, a liquid phase of H2SO4 was found to exist at the grain boundaries and triple junctions of the doped ice, which is thought to have significantly contributed towards its reduced viscosity. Because snow is often considered to be a more porous version of solid ice, these results are thought to be of significance for better understanding the mechanics and viscous deformation of snowpacks as well, warranting further investigation. These snowbased investigations are now underway at the Subzero Research Laboratory at Montana State University.
Object ID: ISSW2018_P10.2.pdf
Language of Article: English
Presenter(s):
Keywords: ice mechanics, snow mechanics, soluble impurities, Raman spectroscopy, micro-CT
Page Number(s): 890-894
-