The creep of polycrystalline ice

Glen, J. W.

doi:10.1098/rspa.1955.0066

Cited by 1,190 publications

(512 citation statements)

References 7 publications

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“…En is the normalized secondary creep rate, E, a, and T are the observed strain rate, stress, and temperature in kelvins during the run, Q is the effective activation energy for creep, R is the gas constant, and the value of the exponent, 3. 2, is that determined by Glen (1955) in similar uniaxial tests on fine-grained ice. (Fig .…”

Section: Proced Urementioning

confidence: 99%

“…Rewriting we obtain B = a /E l / n = exay where ay is the yield strength and ex is a constant of proportionality. In clean ice at the pressure melting point the yield strength is about I bar (Nye, 1951 , p. 559), and B is about 2 bar year l /" (Glen, 1955), so ex is approximately 2 yearl /n. Experimental values of ay (Table I ) are calculated assuming a value of 3.2 for n. The increase in yield strength due to the dispersed particles, (a y-a ym ) , is typically I to 2 bars, where aym is the yield strength of the pure matrix (runs I, 3, and 4) .…”

Section: 32 I)mentioning

confidence: 99%

“…Because there were slight differences in temp erature and stress b etween runs, all strainrates were normalized to a stress of 5.6 bar and a temperature of -9. which is based on Glen's flow law and the Arrhenius equation (Glen, 1955). En is the normalized secondary creep rate, E, a, and T are the observed strain rate, stress, and temperature in kelvins during the run, Q is the effective activation energy for creep, R is the gas constant, and the value of the exponent, 3.…”

Section: Proced Urementioning

confidence: 99%

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Creep of Ice Containing Dispersed Fine Sand

1972

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ABSTRACT. Cylindrical sa mples of ice with 0.0 to 0.35 volume fraction fine sand were tested in un confin ed un iaxial compression at stresses between 5.3 and 6.4 bar and a t tem peratures between -7.4 a nd -9.4° C. Secondary c reep ra tes were obtained from the slope 0(' the total stra in vs. time curve and were normalized to 5.6 bar and -g. 1 0 C. Creep rates in ice with low sand concentra tions were in some cases bigber a nd in otber cases lower tban in clean ice. H owever at high er sand concentrations the creep rate decreases exponentiall y with inc reasing volu me frac tion sa nd . Tbe la tter results a re in general agreement with theories d eveloped to expla in dispersion hard ening of metals, and suggest tbat eac h sand grain is surrounded by a tangled network of second ar y disloca tions which impede passage of prima ry glide dislocations. R ESUME. FIlIage de la glace con tenant un sable fin en dispersion. On a tes te d es ec han tillo ns cylindriques de glace contenant 0,0 a. 0,35 fois son volume de sabl e fin en les soumettant a une compression uniaxia le comprise entre 5,3 et 6,4 bar et a un e temperature comprise entre -7,4 et -9,4° C. La vitesse de Auage second a ire fut o btenue a. partir de la pente de la courbe d onn an t la deform a ti on to tale en fon ction du tem ps et fut normalisee a. donn er la vitesse a. 5,6 bar e t -g, 1 0 C. L es vitesses d e Auage dans la glace a. fa ible concentration

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Section: Proced Urementioning

confidence: 99%

Section: 32 I)mentioning

confidence: 99%

Section: Proced Urementioning

confidence: 99%

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Creep of Ice Containing Dispersed Fine Sand

1972

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“…Depending on the creep mechanism and the stress magnitude, values from n = 1 to n = 4 are appropriate (Steinemann, 1954;Durham and others, 1997;Goldsby and Kohlstedt, 2001). We take n = 3 following Glen (1955), as is common in glaciology. We give representative values for parameters in Table 1.…”

Section: Classical R-channel Theorymentioning

confidence: 99%

Effects of ice deformation on Röthlisberger channels and implications for transitions in subglacial hydrology

et al. 2016

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ABSTRACT. Along the base of glaciers and ice sheets, the sliding of ice over till depends critically on water drainage. In locations where drainage occurs through Röthlisberger channels, the effective pressure along the base of the ice increases and can lead to a strengthening of the bed, which reduces glacier sliding. The formation of Röthlisberger channels depends on two competing effects: (1) melting from turbulent dissipation opens the channel walls and (2) creep flow driven by the weight of the overlying ice closes the channels radially inward. Variation in downstream ice velocity along the channel axis, referred to as an antiplane shear strain rate, decreases the effective viscosity. The softening of the ice increases creep closure velocities. In this way, even a modest addition of antiplane shear can double the size of the Röthlisberger channels for a fixed water pressure or allow channels of a fixed radius to operate at lower effective pressure, potentially decreasing the strength of the surrounding bed. Furthermore, we show that Röthlisberger channels can be deformed away from a circular cross section under applied antiplane shear. These results can have broad impacts on sliding velocities and potentially affect the total ice flux out of glaciers and ice streams.

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“…Under the SIA (Hutter, 1983) with a non-linear rheology for ice, namely the Glen's flow power law with exponent n = 3 (Glen, 1955), Equation (1) can be written as the diffusion equation…”

Section: Adi and Si Schemes 21 Main Equations Of The Model Within Tmentioning

confidence: 99%

Improvement of a 2-D SIA ice-flow model: application to Glacier de Saint-Sorlin, France

Schäfer

Meur

2007

J. Glaciol.

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ABSTRACT. A number of improvements have been made to an existing two-dimensional ice-flow model applied to an alpine glacier. Analysis of the results of the existing model revealed several shortcomings. The first concerns the lack of mass conservation of the applied alternating-direction-implicit (ADI) scheme. A semi-implicit (SI) scheme is therefore proposed and the effects on mass conservation assessed by a comparison with the ADI scheme. The comparison is first carried out with a simple theoretical glacier for which the improvement is significant. Concerning the real case of Glacier de Saint-Sorlin, France, the initial deviation in mass conservation was much less pronounced such that the new scheme, although improving mass conservation, does not significantly change the modelled dynamics. However, other shortcomings that have a more profound impact on the modelling of glacier behaviour have been identified. The ice thickness may become negative over some gridpoints, leading to an inconsistency. The problem is partly resolved by incorporating extra checks on critical gridpoints at the glacier border. Finally, with the help of ice particle tracking, unrealistic ice settlement above the bergschrund has been identified as the main reason for spurious dynamic effects and has been corrected.

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The creep of polycrystalline ice

Cited by 1,190 publications

References 7 publications

Creep of Ice Containing Dispersed Fine Sand

Creep of Ice Containing Dispersed Fine Sand

Effects of ice deformation on Röthlisberger channels and implications for transitions in subglacial hydrology

Improvement of a 2-D SIA ice-flow model: application to Glacier de Saint-Sorlin, France

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