Detection and quantification of permafrost change in alpine rock walls and implications for rock instability
The perennial presence of ice in permafrost rock walls alters thermal, hydraulic and mechanic properties of the rock mass. Temperature-related changes in both, rock mechanical properties (compressive and tensile strength of water-saturated rock) and ice mechanical properties (creep, fracture and coh...
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Universitäts- und Landesbibliothek Bonn
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ftunivbonn:oai:bonndoc.ulb.uni-bonn.de:20.500.11811/4117 2023-05-15T16:36:45+02:00 Detection and quantification of permafrost change in alpine rock walls and implications for rock instability Krautblatter, Michael Dikau, Richard Haeberli, Willy 2010-01-08 application/pdf https://hdl.handle.net/20.500.11811/4117 eng eng Universitäts- und Landesbibliothek Bonn info:eu-repo/semantics/altIdentifier/urn/urn:nbn:de:hbz:5N-18389 https://hdl.handle.net/20.500.11811/4117 In Copyright http://rightsstatements.org/vocab/InC/1.0/ openAccess ddc:910 doc-type:doctoralThesis 2010 ftunivbonn https://doi.org/20.500.11811/4117 2023-02-13T19:27:28Z The perennial presence of ice in permafrost rock walls alters thermal, hydraulic and mechanic properties of the rock mass. Temperature-related changes in both, rock mechanical properties (compressive and tensile strength of water-saturated rock) and ice mechanical properties (creep, fracture and cohesive properties) account for the internal mechanical destabilisation of permafrost rocks. Two hypothetical ice-/rock mechanical models were developed based on the principle of superposition. Failure along existing sliding planes is explained by the impact of temperature on shear stress uptake by creep deformation of ice, the propensity of failure along rock-ice fractures and reduced total friction along rough rock-rock contacts. This model may account for the rapid response of rockslides to warming (reaction time). In the long term, brittle fracture propagation is initialised. Warming reduces the shear stress uptake by total friction and decreases the critical fracture toughness along rock bridges. The latter model accounts for slow subcritical destabilisation of whole rock slopes over decades to millennia, subsequent to the warming impulse (relaxation time). To gain further understanding of thermal, hydraulic and mechanic properties of permafrost rocks, multidimensional and multi-temporal insights into the system are required. This Ph.D. adopted, modified and calibrated existing ERT (electrical resistivity tomography) techniques for the use in permafrost rocks. Laboratory analysis of electrical properties of eight rock samples from permafrost summits brought upon evidence that the general exponential temperature-resistivity relation, proposed by McGinnis (1973), is not applicable for frozen rocks, due to the effects of freezing in confined space. We found, that separate linear temperature-resistivity (T- ρ) approximation of unfrozen, supercooled and frozen behaviour offers a better explanation of the involved physics. Frozen T-ρ gradients approach 29.8 ±10.6 %/°C while unfrozen gradients were confirmed at 2.9 ±0.3 ... Doctoral or Postdoctoral Thesis Ice permafrost bonndoc - The Repository of the University of Bonn |
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bonndoc - The Repository of the University of Bonn |
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English |
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ddc:910 Krautblatter, Michael Detection and quantification of permafrost change in alpine rock walls and implications for rock instability |
topic_facet |
ddc:910 |
description |
The perennial presence of ice in permafrost rock walls alters thermal, hydraulic and mechanic properties of the rock mass. Temperature-related changes in both, rock mechanical properties (compressive and tensile strength of water-saturated rock) and ice mechanical properties (creep, fracture and cohesive properties) account for the internal mechanical destabilisation of permafrost rocks. Two hypothetical ice-/rock mechanical models were developed based on the principle of superposition. Failure along existing sliding planes is explained by the impact of temperature on shear stress uptake by creep deformation of ice, the propensity of failure along rock-ice fractures and reduced total friction along rough rock-rock contacts. This model may account for the rapid response of rockslides to warming (reaction time). In the long term, brittle fracture propagation is initialised. Warming reduces the shear stress uptake by total friction and decreases the critical fracture toughness along rock bridges. The latter model accounts for slow subcritical destabilisation of whole rock slopes over decades to millennia, subsequent to the warming impulse (relaxation time). To gain further understanding of thermal, hydraulic and mechanic properties of permafrost rocks, multidimensional and multi-temporal insights into the system are required. This Ph.D. adopted, modified and calibrated existing ERT (electrical resistivity tomography) techniques for the use in permafrost rocks. Laboratory analysis of electrical properties of eight rock samples from permafrost summits brought upon evidence that the general exponential temperature-resistivity relation, proposed by McGinnis (1973), is not applicable for frozen rocks, due to the effects of freezing in confined space. We found, that separate linear temperature-resistivity (T- ρ) approximation of unfrozen, supercooled and frozen behaviour offers a better explanation of the involved physics. Frozen T-ρ gradients approach 29.8 ±10.6 %/°C while unfrozen gradients were confirmed at 2.9 ±0.3 ... |
author2 |
Dikau, Richard Haeberli, Willy |
format |
Doctoral or Postdoctoral Thesis |
author |
Krautblatter, Michael |
author_facet |
Krautblatter, Michael |
author_sort |
Krautblatter, Michael |
title |
Detection and quantification of permafrost change in alpine rock walls and implications for rock instability |
title_short |
Detection and quantification of permafrost change in alpine rock walls and implications for rock instability |
title_full |
Detection and quantification of permafrost change in alpine rock walls and implications for rock instability |
title_fullStr |
Detection and quantification of permafrost change in alpine rock walls and implications for rock instability |
title_full_unstemmed |
Detection and quantification of permafrost change in alpine rock walls and implications for rock instability |
title_sort |
detection and quantification of permafrost change in alpine rock walls and implications for rock instability |
publisher |
Universitäts- und Landesbibliothek Bonn |
publishDate |
2010 |
url |
https://hdl.handle.net/20.500.11811/4117 |
genre |
Ice permafrost |
genre_facet |
Ice permafrost |
op_relation |
info:eu-repo/semantics/altIdentifier/urn/urn:nbn:de:hbz:5N-18389 https://hdl.handle.net/20.500.11811/4117 |
op_rights |
In Copyright http://rightsstatements.org/vocab/InC/1.0/ openAccess |
op_doi |
https://doi.org/20.500.11811/4117 |
_version_ |
1766027080737226752 |