In situ sensing guided geotechnical modelling of subglacial deformation
In situ sensing guided geotechnical modelling of subglacial deformation
Data collected by in situ subglacial probes has been used to guide a series of geotechnical tests on till. The testing provides an opportunity to develop a process-based understanding of movement patterns observed in the subglacial environment. The probes were deployed by the Glacsweb project at Skalafellsjökull, Iceland, in 2008 and 2012. They were emplaced in till below 80 m of ice and recorded a number of variables including pore pressure, case stress, movement and conductivity. During the winter of 2008-2009 cyclic pressure changes were recorded in the till. Repeated pore pressure increases of up to 20% occurred over a variable period of one to eight weeks. Each rise was followed by a sharp drop in pore pressure lasting up to a few days. A back pressure shear box was used to replicate the pore pressure changes whilst maintaining a constant horizontal shear stress and normal total stress to examine effects on deformation and strain rate. Till was collected for testing from the ice margin close to the probes in 2012 and remoulded for use in the back pressure shear box. General characterisation of the till was performed to benchmark it against previous work and then a series of pore pressure re-inflation tests were undertaken. These approximated the pore pressure variations observed in the field by linearly increasing pore pressure and so decreasing normal effective stress. The till displayed dilatancy-induced episodic increases in strain rate. These were regulated by consolidation that increased shear strength and so reduced strain rate. Strain rate variations were similar to ice velocity variations recorded by differential GPS deployed on the ice surface above the probes.
Hart, Jane
e949a885-7b26-4544-9e15-32ba6f87e49a
December 2014
Hart, Jane
e949a885-7b26-4544-9e15-32ba6f87e49a
Hart, Jane
(2014)
In situ sensing guided geotechnical modelling of subglacial deformation.
American Geophysical Union, Fall Meeting 2014, , San Francisco, United States.
15 - 19 Dec 2014.
Record type:
Conference or Workshop Item
(Other)
Abstract
Data collected by in situ subglacial probes has been used to guide a series of geotechnical tests on till. The testing provides an opportunity to develop a process-based understanding of movement patterns observed in the subglacial environment. The probes were deployed by the Glacsweb project at Skalafellsjökull, Iceland, in 2008 and 2012. They were emplaced in till below 80 m of ice and recorded a number of variables including pore pressure, case stress, movement and conductivity. During the winter of 2008-2009 cyclic pressure changes were recorded in the till. Repeated pore pressure increases of up to 20% occurred over a variable period of one to eight weeks. Each rise was followed by a sharp drop in pore pressure lasting up to a few days. A back pressure shear box was used to replicate the pore pressure changes whilst maintaining a constant horizontal shear stress and normal total stress to examine effects on deformation and strain rate. Till was collected for testing from the ice margin close to the probes in 2012 and remoulded for use in the back pressure shear box. General characterisation of the till was performed to benchmark it against previous work and then a series of pore pressure re-inflation tests were undertaken. These approximated the pore pressure variations observed in the field by linearly increasing pore pressure and so decreasing normal effective stress. The till displayed dilatancy-induced episodic increases in strain rate. These were regulated by consolidation that increased shear strength and so reduced strain rate. Strain rate variations were similar to ice velocity variations recorded by differential GPS deployed on the ice surface above the probes.
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Published date: December 2014
Venue - Dates:
American Geophysical Union, Fall Meeting 2014, , San Francisco, United States, 2014-12-15 - 2014-12-19
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Local EPrints ID: 432536
URI: http://eprints.soton.ac.uk/id/eprint/432536
PURE UUID: ef147b12-5289-4a48-99e5-b19826b06ff5
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Date deposited: 17 Jul 2019 16:30
Last modified: 23 Feb 2023 02:34
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