The Shear Strength Characteristics of Frozen Coarse Granular Debris

Nickling, W. G.; Bennett, Lorne

doi:10.3189/s0022143000006201

Cited by 32 publications

(25 citation statements)

References 12 publications

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“…Subsequent work extended the range of debris and ice concentrations to ice‐rich and ice‐poor debris and indicated that the composite reached a peak strength at high debris concentration but became weaker as the mixture became more ice‐poor [ Baker , ]. A similar result was found in higher‐temperature direct shear experiments on undisturbed rock glacier material from the Yukon, Canada, though the relative increase in strength was subdued compared to colder experiments [ Nickling and Bennett , ]. In most of these experiments, the peak strength corresponded to a relatively high debris concentration and when the pore spaces were completely filled with ice, and this strength was only weakly sensitive to the rate of deformation for temperatures below −5°C [ Baker , ; Parameswaran , ; Baker and Jones , ].…”

Section: Experimental Constraintssupporting

confidence: 65%

Deformation of debris-ice mixtures

2014

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Mixtures of rock debris and ice are common in high-latitude and high-altitude environments and are thought to be widespread elsewhere in our solar system. In the form of permafrost soils, glaciers, and rock glaciers, these debris-ice mixtures are often not static but slide and creep, generating many of the landforms and landscapes associated with the cryosphere. In this review, a broad range of field observations, theory, and experimental work relevant to the mechanical interactions between ice and rock debris are evaluated, with emphasis on the temperature and stress regimes common in terrestrial surface and near-surface environments. The first-order variables governing the deformation of debris-ice mixtures in these environments are debris concentration, particle size, temperature, solute concentration (salinity), and stress. A key observation from prior studies, consistent with expectations, is that debris-ice mixtures are usually more resistant to deformation at low temperatures than their pure end-member components. However, at temperatures closer to melting, the growth of unfrozen water films at ice-particle interfaces begins to reduce the strengthening effect and can even lead to profound weakening. Using existing quantitative relationships from theoretical and experimental work in permafrost engineering, ice mechanics, and glaciology combined with theory adapted from metallurgy and materials science, a simple constitutive framework is assembled that is capable of capturing most of the observed dynamics. This framework highlights the competition between the role of debris in impeding ice creep and the mitigating effects of unfrozen water at debris-ice interfaces.

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Section: Experimental Constraintssupporting

confidence: 65%

Deformation of debris-ice mixtures

2014

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“…Tests using samples prepared by mixing crushed ice, water at 0 °C and soil yielded results similar to those of Baker () (e.g. Goughnour and Andersland, ; Nickling and Bennett, ). Arenson et al .…”

Section: Introductionsupporting

confidence: 70%

The Effect of Confining Pressure and Water Content on Compressive Strength and Deformation of Ice-Rich Silty Sand

Zhang

Harbor

2016

Permafrost and Periglac. Process.

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The characteristics of ice‐rich frozen soils are important to engineering design in cold‐climate regions. Previous work has concentrated on uniaxial strength properties, and limited data exist on triaxial strength and deformation as a function of volumetric ice content and confining pressure. Triaxial compressive tests carried out on ice‐rich frozen silty sand indicated that the strength decreases to a minimum and then increases up to that of pure ice for a range of volumetric ice contents. However, the effect of confining pressure on the strength depends on the volumetric ice content itself. The strength was at a nearly constant minimum level when the volumetric ice content was between 48.2 and 65.1 per cent, dominated by the cohesion of the ice matrix. In contrast, at volumetric ice contents of > 27.2 to < 50.2 per cent and > 80.9 per cent, the strength increased with increasing confining pressure. The volumetric ice contents corresponding to maximum failure strain and minimum strength were 50.2 and 61.9 per cent, respectively. Thus, in this range an increase of about 10 per cent in volumetric ice content causes the failure strain to drop to the value for pure ice. The results indicate that there is a transition zone when the volumetric ice content is between 50.2 and 61.9 per cent that separates sample behaviour from that of frozen soil to that of pure ice. Copyright © 2016 John Wiley & Sons, Ltd.

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“…Very few rheological experiments have been reported on debris-bearing ice, and these have yielded diverse and sometimes contradictory results. Work on different types of debris-bearing ice led to the conclusion that the presence of debris could either strengthen or soften the ice, depending on the concentration, granulometry, and distribution of debris particles [e.g., Holdsworth, 1974;Nickling and Bennett, 1984;Echelmeyer and Zhongxiang, 1987;Waller and Hart, 1999;Fitzsimons et al, 2001]. A hint to our question here may be given by strain experiments on basal ice samples from Taylor Glacier.…”

Section: Rheological Contrastsmentioning

confidence: 99%

Dynamic implications of discontinuous recrystallization in cold basal ice: Taylor Glacier, Antarctica

2008

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Crystallographic investigations have been conducted of cold (−17°C) debris‐bearing ice from the base of an Antarctic outlet glacier (Taylor Glacier). The 4‐m‐thick sequence studied has been retrieved from a 20‐m‐long tunnel dug from the glacier snout and has been analyzed with an automatic ice fabric analyzer (AIFA). The top and bottom of the sequence consists of clean meteoric ice (englacial facies), whereas alternating debris‐rich and clean bubbly ice layers are found in the middle part (stratified facies). Ice from the englacial facies displays a polygonal texture and a strong c‐axis clustering toward the vertical, denoting recrystallization through “subgrain rotation” (SGR). In contrast, clean ice from the stratified facies shows SGR fabrics which are delimited at the contact with debris‐rich layers by large, interlocking grains organized in ribbons. These two distinct textures within the stratified facies are associated with looser c‐axis patterns at the scale of single thin sections, which is interpreted as resulting from “migration recrystallization” (MR). The change from SGR to MR trends marks a clear increase in grain boundary and nucleation kinetics (hence the term “discontinuous recrystallization”) and may be associated with strain localization at rheological interfaces during basal ice genesis. Analogies with bottom ice from deep polar ice sheets, where temperature is commonly higher than at the studied site, are highlighted. Two recrystallization scenarios are proposed, accounting for the development of both types of fabrics. It is shown that by controlling the repartition of stress and strain energy within basal ice, the rheology of debris‐bearing ice layers plays a decisive role in recrystallization dynamics at structural interfaces. We also demonstrate how the same recrystallization regimes may occur in cold glaciers and temperate ice sheets, provided that strain accumulation has been high enough in the former. This challenges the common belief that migration fabrics observed in bottom ice from deep ice sheets are exclusive to warm, stagnant, annealed ice.

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The Shear Strength Characteristics of Frozen Coarse Granular Debris

Cited by 32 publications

References 12 publications

Deformation of debris-ice mixtures

Deformation of debris-ice mixtures

The Effect of Confining Pressure and Water Content on Compressive Strength and Deformation of Ice-Rich Silty Sand

Dynamic implications of discontinuous recrystallization in cold basal ice: Taylor Glacier, Antarctica

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