Project

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Paraglacial Rock Slope Mechanics

English title Paraglacial Rock Slope Mechanics
Applicant Löw Simon
Number 135184
Funding scheme Project funding
Research institution Geologisches Institut ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Other disciplines of Earth Sciences
Start/End 01.06.2011 - 30.09.2013
Approved amount 282'271.00
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All Disciplines (2)

Discipline
Other disciplines of Earth Sciences
Civil Engineering

Keywords (3)

Landslide; Glacial Retreat; Aletsch Glacier

Lay Summary (German)

Lead
"Am Ende der Eiszeit fanden, ausgelöst durch den Rückzug der Talgletscher, viele Bergstürze statt". Diese Hypothese ist weitverbreitet aber wenig wissenschaftlich untersucht und möglicherweise auch falsch.
Lay summary
In diesem von Schweizerischen Nationalfonds seit 10 Jahren finanzierten Projekt werden im Gebiet des grossen Aletschgletschers die Interkationen zwischen dem sich zurückziehenden Talgletscher und den umgebenden Talflanken – inklusive der spektakulären Rutschung von Moosfluh -  im Detail untersucht.
Die Arbeiten umfassen umfangreiche Messungen von Deformationen an der Geländeoberfläche und in Bohrungen, welche mit möglichen Ursachen (Umweltfaktoren) verglichen werden. Sehr wichtige und an mehreren Stationen erfasste Umweltfaktoren sind Niederschlag (in Form von Regen und Schnee), Temperatur und der Rückzug des Grossen Aletschgletschers. Diese Umweltfaktoren beeinflussen Wasserdrucke, Spannungen sowie die Bildung von Rissen in den felsigen Talflanken. Durch ein verbessertes Verständnis dieser physikalischen Zusammenhänge kann anschliessend mit Computermodellen die langfristige Entwicklung dieser Talflanken seit der letzten Eiszeit vor 20'000 Jahren sowie die Entstehung von Hanginstabilitäten (Rutschungen, Bergstürze) in geologischen Zeiträumen erklärt sowie auch in die Zukunft prognostiziert werden.

Direct link to Lay Summary Last update: 27.09.2019

Lay Summary (English)

Lead
Glacial erosion deepens alpine valley floors and steepens the adjacent rock slopes. With glacier retreat, rock walls are often exposed in an over-steepened state and prone to collapse. Glacial cycles act rapidly on the geologic time scale to alter the boundary conditions of a rock slope, exposing bedrock to varying surface temperature, pore pressure and moisture conditions and changing the internal state of stress as the buttressing support of glacier ice changes through time. The response of alpine valley rock walls to these changing boundary conditions is intimately tied to both the material properties and the rate and magnitude of stress changes. Our project attempts to clarify the role of rock and fracture mechanical attributes on the paraglacial slope response in glaciated and actively deglaciating landscapes in a study area around the tongue of the Great Aletsch Glacier.
Lay summary

Glacial erosiondeepens alpine valley floors and steepens the adjacent rock slopes. Withglacier retreat, rockwalls are often exposed in an over-steepened state andprone to collapse. “Paraglacial processes” refer to non-glacial processes (e.g.rockfall & rockslides) that are directly conditioned by cycles ofglaciation and deglaciation. Such cycles act rapidly on the geologic time scaleto alter the boundary conditions of a rock slope, exposing bedrock to varyingsurface temperature and moisture conditions and changing the internal state ofstress as the buttressing support of glacier ice changes through time. Theresponse of alpine valley rockwalls to these changing boundary conditions isintimately tied to both the material properties and the rate and magnitude ofstress changes. Our project attempts to clarify the role of rock and fracture mechanicalattributes on the paraglacial slope response in glaciated and activelydeglaciating landscapes in a study area between the Grimsel Pass and Aletschglacier. Through the contained tasks this project will contribute to advancesin a number of fundamental themes. First, as an overall goal we will testmodels of paraglacial conditioning and associated spatial / temporal rock sloperesponse – e.g. when and where do slope failures or new fracture systemsdevelop? Next we analyze rock slope activityassociated with a changing climate, in the time since the Last Glacial Maximumand the present with potential outcomes for future assessment. Further, aseries of fundamental scientific questions will be addressed, such as what arethe detailed mechanisms driving formation of exfoliation fractures in graniticrocks, what is the temporal variability of landslide activity in the study areasince the Last Glacial Maximum, and what are the dominant hydro-mechanicalfactors controlling the rock slope response to ongoing deglaciation? Thebroader impact of this project, however, reaches beyond the scientificcommunity. For example real implications for natural hazard assessment areimplicit in our research, as this project offers a broad framework forunderstanding processes associated with the development of alpine rock slopeinstabilities, especially related to climate warming and glacier retreat. Other practical applications of the scientific results of this project are related to the occurrence and properties of exfoliation fractures which are critical for underground excavations such as traffic tunnels or hydropower systems.
Direct link to Lay Summary Last update: 27.09.2019

Responsible applicant and co-applicants

Employees

Publications

Publication
Near-surface rock stress orientations in alpine topography derived from exfoliation fracture surface markings and 3D numerical modelling
Ziegler Martin, Loew Simon, Amann Florian (2016), Near-surface rock stress orientations in alpine topography derived from exfoliation fracture surface markings and 3D numerical modelling, in INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES, 85, 129-151.
Growth of exfoliation joints and near-surface stress orientations inferred from fractographic markings observed in the upper Aar valley (Swiss Alps)
Ziegler Martin, Loew Simon, Bahat Dov (2014), Growth of exfoliation joints and near-surface stress orientations inferred from fractographic markings observed in the upper Aar valley (Swiss Alps), in TECTONOPHYSICS, 626, 1-20.
Distribution and inferred age of exfoliation joints in the Aar Granite of the central Swiss Alps and relationship to Quaternary landscape evolution
Ziegler Martin, Loew Simon, Moore Jeffrey (2013), Distribution and inferred age of exfoliation joints in the Aar Granite of the central Swiss Alps and relationship to Quaternary landscape evolution, in GEOMORPHOLOGY, 201, 344-362.
Pore pressure distributions in brittle translational rockslides
Loew Simon, Strauhal Thomas (2013), Pore pressure distributions in brittle translational rockslides, in Italian Journal of Engineering Geology and Environment, 165-175.
Monitoring of potentially catastrophic rockslides
Loew Simon, Gischig Valentin, Moore Jeffrey, Keller-Signer Alexandra (2012), Monitoring of potentially catastrophic rockslides, in Landslides and Engineered Slopes: Protecting Society through Improved Understanding, BanffTaylor & Francis Group, London.
Randa: Kinematics and driving mechanisms of a large complex rockslide
Loew Simon, Gischig Valentin, Willenberg Heike, Alpiger Andrea, Moore Jeffrey (2012), Randa: Kinematics and driving mechanisms of a large complex rockslide, in Clague John (ed.), Cambridge, Cambridge, 297-309.
Reversible rock-slope deformations caused by cyclic water-table fluctuations in mountain slopes of the Central Alps, Switzerland
Hansmann Jürgen, Loew Simon, Evans Keith (2012), Reversible rock-slope deformations caused by cyclic water-table fluctuations in mountain slopes of the Central Alps, Switzerland, in Hydrogeology Journal, 20, 73-91.
Air circulation in deep fractures and the temperature field of an alpine rock slope
Moore JR, Gischig V, Katterbach M, Loew S (2011), Air circulation in deep fractures and the temperature field of an alpine rock slope, in EARTH SURFACE PROCESSES AND LANDFORMS, 36(15), 1985-1996.
Composite rock slope kinematics at the current Randa instability, Switzerland, based on remote sensing and numerical modeling
Gischig V, Amann F, Moore JR, Loew S, Eisenbeiss H, Stempfhuber W (2011), Composite rock slope kinematics at the current Randa instability, Switzerland, based on remote sensing and numerical modeling, in ENGINEERING GEOLOGY, 118(1-2), 37-53.
Site Effects in Unstable Rock Slopes: Dynamic Behavior of the Randa Instability (Switzerland)
Moore JR, Gischig V, Burjanek J, Loew S, Fah D (2011), Site Effects in Unstable Rock Slopes: Dynamic Behavior of the Randa Instability (Switzerland), in BULLETIN OF THE SEISMOLOGICAL SOCIETY OF AMERICA, 101(6), 3110-3116.
Thermomechanical forcing of deep rock slope deformation: 1. Conceptual study of a simplified slope
Gischig VS, Moore JR, Evans KF, Amann F, Loew S (2011), Thermomechanical forcing of deep rock slope deformation: 1. Conceptual study of a simplified slope, in JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE, 116(F04010), 1-18.
Thermomechanical forcing of deep rock slope deformation: 2. The Randa rock slope instability
Gischig VS, Moore JR, Evans KF, Amann F, Loew S (2011), Thermomechanical forcing of deep rock slope deformation: 2. The Randa rock slope instability, in JOURNAL OF GEOPHYSICAL RESEARCH-EARTH SURFACE, 116(F04011), 1-17.
Multidisciplinary monitoring of progressive failure processes in brittle rock slopes
Loew Simon, Gischig Valentin, Glüer Franziska, Seifert Reto, Moore Jeffres, Multidisciplinary monitoring of progressive failure processes in brittle rock slopes, in Xia-Ting Feng (ed.), CRC Press / Balkema, Leiden, 629-662.

Collaboration

Group / person Country
Types of collaboration
University of Utah United States of America (North America)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
Versuchsanstalt für Wasserbau Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure
Institut für Geodäsie und Photogrammetrie Switzerland (Europe)
- in-depth/constructive exchanges on approaches, methods or results
- Publication
- Research Infrastructure

Communication with the public

Communication Title Media Place Year
Media relations: print media, online media Der Gletscher schlägt zurück NZZ Am Sonntag Western Switzerland German-speaking Switzerland 2016
Media relations: print media, online media Guten Rutsch Süddeutsche Zeitung International 2016
Print (books, brochures, leaflets) Jubiläums-Ausstellung 150 Jahre Swiss Re: Protecting Generations International 2013
Media relations: radio, television 10vor10 SF DRS German-speaking Switzerland 2012
Media relations: radio, television Nachrichten Radio DRS Italian-speaking Switzerland 2012

Awards

Title Year
ETH Silver Medal for PhD of Valentin Gischig (Randa) 2012
AGU Graduate Research Award for PhD of Valentin Gischig (Randa) 2011

Associated projects

Number Title Start Funding scheme
172492 Paraglacial Rock Slope Mechanics (Phase III) 01.04.2017 Project funding
172492 Paraglacial Rock Slope Mechanics (Phase III) 01.04.2017 Project funding
146593 Paraglacial Rock Slope Mechanics (Phase II) 01.10.2013 Project funding

Abstract

Cycles of glacial erosion and retreat expose Alpine valley rockwalls in an oversteepened, meta-stable state. The subsequent rock slope response will vary with changing in-situ stress conditions, material properties, slope geometry and local environmental conditions, and may include generation of new fractures, gravitational deformation, or catastrophic collapse. Although paraglacial rock slope failures are among the fastest and most dramatic elements of the landscape response to erosion and deglaciation, large unknowns remain relating to key themes of underlying failure processes, controlling parameters, and instability distributions. This study presents a comprehensive research plan aimed to critically evaluate the response and instability characteristics of rockwalls subjected to glacial erosion and debuttressing associated with repeated cycles of Quaternary glaciation. We bring a solid background in landslide analysis, rock mechanics and rock slope hydraulics, and focus our attention specifically on complex interactions between valley glaciers, rock slopes, and the local Alpine environment. The project considers three main time scales and slope reactions in detail: 1) Pleistocene glacial erosion and exfoliation fracturing in massive rocks, 2) Late Glacial rock slope response and rock mass strength degradation, and 3) On-going rock slope response related to recent glacial retreat. Each theme will be addressed through three interrelated PhD projects, and the envisioned PhD students will cooperate intensively. The study area selected for this project is in the central Swiss Alps in the region between the Aletsch glacier in the west and the Unteraar glacier in the east (Figs 1-3).PhD project 1 aims to improve our understanding of exfoliation joint formation, including details of fracture processes and relevant time scales, which remain controversial today. The study area of this project - especially the Grimsel Pass area - is well suited to study the 3D geometry of exfoliation fractures (both at ground surface and in galleries), to assess in-situ stress conditions, and to relate fracturing to erosional surfaces from different time periods. PhD project 2 will focus on investigating mechanical controls on the regional distribution of paraglacial rock slope failures. This sub-project will be strongly based on field observations documenting rockslide occurrence, glacier extents at key stages, and variations in rock mass properties. Following quantitative analyses will explore correlations between the landslide distribution and mapped ice levels, 3D near-surface stress changes, and time-dependent rock mass strength properties. PhD project 3 will include detailed monitoring of ongoing slope deformations associated with an actively retreating glacier, and on understanding the underlying processes forcing these moments and how they relate to glacier dynamics. The study area of this project - especially the Aletsch glacier - offers the unique opportunity to relate current slope movements and recent failures to well-constrained glacier retreat. We will focus on the latest monitoring methods with large spatial coverage and high resolution (i.e. ground-based radar interferometry) complemented with in-situ measurements. All field data will be interpreted with numerical models to improve our understanding of brittle rock mass behavior and exfoliation joint formation, factors controlling the distribution of paraglacial rock slope failures, and ongoing processes of slope deformation in actively deglaciating environments.
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