A new methodology to simulate subglacial deformation of water-saturated granular material
The dynamics of glaciers are to a large degree governed by processes operating at the ice–bed interface, and one of the primary mechanisms of glacier flow over soft unconsolidated sediments is subglacial deformation. However, it has proven difficult to constrain the mechanical response of subglacial...
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Copernicus Publications
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fttriple:oai:gotriple.eu:oai:doaj.org/article:8181040c65034bb1a6e614b500ffdb8b 2023-05-15T18:32:21+02:00 A new methodology to simulate subglacial deformation of water-saturated granular material A. Damsgaard D. L. Egholm J. A. Piotrowski S. Tulaczyk N. K. Larsen C. F. Brædstrup 2015-11-01 https://doi.org/10.5194/tc-9-2183-2015 http://www.the-cryosphere.net/9/2183/2015/tc-9-2183-2015.pdf https://doaj.org/article/8181040c65034bb1a6e614b500ffdb8b en eng Copernicus Publications 1994-0416 1994-0424 doi:10.5194/tc-9-2183-2015 http://www.the-cryosphere.net/9/2183/2015/tc-9-2183-2015.pdf https://doaj.org/article/8181040c65034bb1a6e614b500ffdb8b undefined The Cryosphere, Vol 9, Iss 6, Pp 2183-2200 (2015) geo envir Journal Article https://vocabularies.coar-repositories.org/resource_types/c_6501/ 2015 fttriple https://doi.org/10.5194/tc-9-2183-2015 2023-01-22T17:51:14Z The dynamics of glaciers are to a large degree governed by processes operating at the ice–bed interface, and one of the primary mechanisms of glacier flow over soft unconsolidated sediments is subglacial deformation. However, it has proven difficult to constrain the mechanical response of subglacial sediment to the shear stress of an overriding glacier. In this study, we present a new methodology designed to simulate subglacial deformation using a coupled numerical model for computational experiments on grain-fluid mixtures. The granular phase is simulated on a per-grain basis by the discrete element method. The pore water is modeled as a compressible Newtonian fluid without inertia. The numerical approach allows close monitoring of the internal behavior under a range of conditions. Our computational experiments support the findings of previous studies where the rheology of a slowly deforming water-saturated granular bed in the steady state generally conforms to the rate-independent plastic rheology. Before this so-called critical state, deformation is in many cases accompanied by volumetric changes as grain rearrangement in active shear zones changes the local porosity. For previously consolidated beds porosity increases can cause local pore-pressure decline, dependent on till permeability and shear rate. We observe that the pore-water pressure reduction strengthens inter-granular contacts, which results in increased shear strength of the granular material. In contrast, weakening takes place when shear deformation causes consolidation of dilated sediments or during rapid fabric development. Both processes of strengthening and weakening depend inversely on the sediment permeability and are transient phenomena tied to the porosity changes during the early stages of shear. We find that the transient strengthening and weakening in turn influences the distribution of shear strain in the granular bed. Dilatant strengthening has the ability to distribute strain during early deformation to large depths, if sediment ... Article in Journal/Newspaper The Cryosphere Unknown The Cryosphere 9 6 2183 2200 |
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English |
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geo envir |
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geo envir A. Damsgaard D. L. Egholm J. A. Piotrowski S. Tulaczyk N. K. Larsen C. F. Brædstrup A new methodology to simulate subglacial deformation of water-saturated granular material |
topic_facet |
geo envir |
description |
The dynamics of glaciers are to a large degree governed by processes operating at the ice–bed interface, and one of the primary mechanisms of glacier flow over soft unconsolidated sediments is subglacial deformation. However, it has proven difficult to constrain the mechanical response of subglacial sediment to the shear stress of an overriding glacier. In this study, we present a new methodology designed to simulate subglacial deformation using a coupled numerical model for computational experiments on grain-fluid mixtures. The granular phase is simulated on a per-grain basis by the discrete element method. The pore water is modeled as a compressible Newtonian fluid without inertia. The numerical approach allows close monitoring of the internal behavior under a range of conditions. Our computational experiments support the findings of previous studies where the rheology of a slowly deforming water-saturated granular bed in the steady state generally conforms to the rate-independent plastic rheology. Before this so-called critical state, deformation is in many cases accompanied by volumetric changes as grain rearrangement in active shear zones changes the local porosity. For previously consolidated beds porosity increases can cause local pore-pressure decline, dependent on till permeability and shear rate. We observe that the pore-water pressure reduction strengthens inter-granular contacts, which results in increased shear strength of the granular material. In contrast, weakening takes place when shear deformation causes consolidation of dilated sediments or during rapid fabric development. Both processes of strengthening and weakening depend inversely on the sediment permeability and are transient phenomena tied to the porosity changes during the early stages of shear. We find that the transient strengthening and weakening in turn influences the distribution of shear strain in the granular bed. Dilatant strengthening has the ability to distribute strain during early deformation to large depths, if sediment ... |
format |
Article in Journal/Newspaper |
author |
A. Damsgaard D. L. Egholm J. A. Piotrowski S. Tulaczyk N. K. Larsen C. F. Brædstrup |
author_facet |
A. Damsgaard D. L. Egholm J. A. Piotrowski S. Tulaczyk N. K. Larsen C. F. Brædstrup |
author_sort |
A. Damsgaard |
title |
A new methodology to simulate subglacial deformation of water-saturated granular material |
title_short |
A new methodology to simulate subglacial deformation of water-saturated granular material |
title_full |
A new methodology to simulate subglacial deformation of water-saturated granular material |
title_fullStr |
A new methodology to simulate subglacial deformation of water-saturated granular material |
title_full_unstemmed |
A new methodology to simulate subglacial deformation of water-saturated granular material |
title_sort |
new methodology to simulate subglacial deformation of water-saturated granular material |
publisher |
Copernicus Publications |
publishDate |
2015 |
url |
https://doi.org/10.5194/tc-9-2183-2015 http://www.the-cryosphere.net/9/2183/2015/tc-9-2183-2015.pdf https://doaj.org/article/8181040c65034bb1a6e614b500ffdb8b |
genre |
The Cryosphere |
genre_facet |
The Cryosphere |
op_source |
The Cryosphere, Vol 9, Iss 6, Pp 2183-2200 (2015) |
op_relation |
1994-0416 1994-0424 doi:10.5194/tc-9-2183-2015 http://www.the-cryosphere.net/9/2183/2015/tc-9-2183-2015.pdf https://doaj.org/article/8181040c65034bb1a6e614b500ffdb8b |
op_rights |
undefined |
op_doi |
https://doi.org/10.5194/tc-9-2183-2015 |
container_title |
The Cryosphere |
container_volume |
9 |
container_issue |
6 |
container_start_page |
2183 |
op_container_end_page |
2200 |
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1766216464865427456 |