The tertiary creep of polycrystalline ice: experimental evidence for stress-dependent levels of strain-rate enhancement

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Abstract:

Laboratory creep deformation experiments have been conducted on initially isotropic laboratory-made samples of polycrystalline ice. Steady-state tertiary creep rates, ∈ter, were determined at strains exceeding 10% in either uniaxial-compression or simple-shear experiments. Isotropic minimum strain rates, ∈min, determined at ∼1% strain, provide a reference for comparing the relative magnitude of tertiary creep rates in shear and compression through the use of strain-rate enhancement factors, E, defined as the ratio of corresponding tertiary and isotropic minimum creep rates, i.e. E = ∈ter/∈min. The magnitude of strain-rate enhancement in simple shear was found to exceed that in uniaxial compression by a constant factor of 2.3. Results of experiments conducted at octahedral shear stresses of τ o = 0.04–0.80 MPa indicate a creep power-law stress exponent of n = 3 for isotropic minimum creep rates and n = 3.5 for tertiary creep rates. The difference in stress exponents for minimum and tertiary creep regimes can be interpreted as a τ o stress-dependent level of strain-rate enhancement, i.e. E α τ 0 1/2. The implications of these results for deformation in complex multicomponent stress configurations and at stresses below those used in the current experiments are discussed.

Document Type: Research Article

DOI: http://dx.doi.org/10.3189/2012JoG11J149

Publication date: April 1, 2012

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  • The Journal of Glaciology is published six times per year. It accepts submissions from any discipline related to the study of snow and ice. All articles are peer reviewed. The Journal is included in the ISI Science Citation Index.
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