MSc Students 2008-2009
Anna Abächerli
Rock Slope Failures Triggered by the Aysen 2007 Earthquake (Southern Chile)
The April 2007 earthquake of Magnitude 6.2 in the Aysen Fjord area (Chile, Patagonian Fjordland, 45.5ºS) triggered hundreds of landslides and several tsunamis in an area of about 10 kilometers around the main shock. The main shock was part of a long lasting seismic activity between January 22 and June 2007 with many thousands of local earthquakes registered (Naranjo et al. 2009; Sepulveda and Serey 2009). The Aysen Fjord is easily accessible by boat and the shore lines and side valleys of the fjord are walkable over substantial distances. The objectives of this ETH subproject, which is part of a large international cooperation, are to improve our understanding of earthquake triggered rockslides in fractured rock masses showing steep topographical gradients. Key issues to be addressed specifically are topographic and material amplifications and earthquake related failure mechanisms of larger (> 10’000 m3) rockslope instabilities composed of fresh and weathered granitic rock masses with multiple fracture sets.
Download extended abstract: Download (PDF, 506 KB) (PDF, 506 KB)
Stijn Bos (ERASMUS)
Franziska Dammeier
Seismic Monitoring and Characterization of Rockfall
Rockfall is one of the principle agents of landscape evolution in the alpine environment and also one of the most prominent distributed hazards in steep terrain. Rockfall from a mountain cliff generates a seismic disturbance as falling blocks strike the wall or other debris en route to the base of the slope. Anomalous vibrations can be monitored with locally emplaced accelerometers, and the seismic response used to identify the timing of rockfall and differentiate between block falls and debris slides. These data may then reveal triggering mechanisms and provide proxy information for estimating event magnitude. This study will focus on using inexpensive and portable seismic monitoring equipment for rockfall event detection and characterization. By comparing environmental and seismic data we hope to identify triggers, characterize different rockfall events, and analyze short and long term trends in rockfall frequency. This research will also critically analyze the potential for use of distributed seismic sensors in rockfall research.
Download extended abstract: Download (PDF, 338 KB) (PDF, 338 KB)
Christian Gartman
Identification of Flow Paths and Travel Times in an Alluvial Aquifer Using Natural Tracer Tests
The goal of this Master Thesis is to identify the flow paths and travel times of young hyporheic groundwater at a restored section of River Thur (Switzerland). As a member of the project group, the student analyzes high-frequency time-series signals for travel-time distributions of up to one month needed for an assessment of the flow field. Concentrations of 222Rn will be analyzed for radon water ages, in the range of two up to two weeks. Small-scale well-to-well tracer tests with dyes (and evtl. heat) will be performed. They help to detect flow paths and to determine the distribution of groundwater flow velocities, effective aquifer porosity, and mixing/solute dispersivity. Basic hydrochemical parameters (major ions) will be monitored periodically, to help to identify mixing ratios of ground waters of a differing origin.
Download extended abstract: Download (PDF, 15 KB) (PDF, 15 KB)
Kenneth Haraldseth (ERASMUS)
Martin Heynen
The Influence of Topographic Amplification and Local Site conditions on the Seismic Stability of Rock Slopes: Seetalhorn, Wallis, Switzerland
Massive earthquake induced rock slope failures in alpine terrains are often associated with mountain peaks. During the 1855 Visp earthquake the peaks above Graechen were associated with rock slope failures ranging from individual blocks to large volume failures (Fritsche et al., 2006). Currently we are involved with a large ETH project investigating geohazards related to Earthquakes (COGEAR). The framework of this thesis is based on this project and aims to investigate the role of the rock mass conditions and topographic amplification on the ground motions induced by earthquakes and how these ground motions influence rock slope stability.
Currently, the Swiss Seismological Service is operating seismometers at five locations near Greachen (including the Seetalhorn) and St Niklaus to measure ground motions associated with nearby earthquakes. Field assessments of the rock mass conditions at 3 of these sites will be used to acquire geological and geotechnical data to help analyze the ground motion data collected by the SED in relation to the rock mass conditions. The area surrounding the Seetalhorn will be used to assess the relationship between ground motions and rock slope stability. This task involves rock mass characterization and the assessment of potential failure modes associated with the rock mass structure. This information will then be used to assess the influence of seismic shaking on the rock mass stability in this area.
Download extended abstract: Download (PDF, 15 KB) (PDF, 15 KB)
Pal Kolstad (ERASMUS)
Peter Müller
The Creeping Rock Slide at Ochsenboden, Switzerland
Planar or compound rock slides in sedimentary sequencies often “creep” on weak layers dipping at shallow angles towards the rock face. In the Helvetic Alps, this is a widespread phenomenon, involving thick limestone bodies creeping on thin marls layers of variable thickness. “Creep” in this context refers to very slow but long duration movements observed during many decades with typical annual mean velocities of less than 1 cm/year. The mechanisms of these rock slides differ fundamentally from brittle rock slope instabilities like Randa; it is expected that such slopes never fail catastrophically. In this MSc project, these creeping mechanisms shall be investigated at an ideal site, called Ochsenboden (Sihl Valley, Switzerland, Swiss Coordinates 715’270/207’946).
Download extended abstract: Download (PDF, 14 KB) (PDF, 14 KB)
Perola Andreas Persson (ERASMUS)
Development of deep-seated slope instabilities in response to active glacier retreat: Aletschglacier, Oberwallis, Switzerland
Retreat of the Aletschglacier has been observed since the end of the little Ice Age (ca. 1850), with accelerated rates occurring in the 1980’s. More recently, repeat-pass satellite SAR interferometry has been used to map the spatio-temporal evolution of a deep-seated instability located in the Aletschwald region of Oberwallis. Satellite InsSAR derived from ERS-1, ERS-2, JERS, ENVISAT, and ALOS have shown accelerated movements occurring since the early 90’s with a rate increase from 3cm/yr to 15cm/yr (Summer 2007). More recently, high resolution TerraSAR-X InSAR has been used to more accurately define the resultant displacement field.
The main goal of this project is to investigate the influence of geological structures in controlling the observed instability and it’s evolution to the measured record of glacier retreat. This is primarily a field based project, which will involve mapping of geological structures, lithology and geomorphic features associated with the deep seated instability. A secondary goal will be to assess the susceptibility of surrounding rock slopes to similar types of instability.
Download extended abstract: Download (PDF, 77 KB) (PDF, 77 KB)
Thomas Schneggenburger
Investigation of a newly discovered mineral water at Samedan (Upper Engadine Valley)
In the village of Samedan a new spa is under construction. During the reconnaissance work with some newly drilled boreholes a new mineral water was discovered. The aim of this investigation is i) to characterize the chemical and isotopic properties of the new discovered mineral water, as ii) also to characterize the hydrogeological flow systems within the context of regional and local geology and tectonics.
Download extended abstract: Download (PDF, 50 KB) (PDF, 50 KB)
Alexandra Signer
Application of a portable microwave radar interferometer for measuring displacments on steep Alpine rock walls: Gornergrat, Wallis, Switzerland
In Summer 2008, a pilot project using a terrestrial radar interferometer was undertaken on the Gornergrat, Canton Wallis, to measure the glacier dynamics related to seasonal draining of the Gornersee. Measurements were made using a real aperture, portable radar interferometer (GPRI). Preliminary results from a 50 minute interferogram (see figure below) demonstrated highly coherent displacements (~4mm) on a nearby 400-500 metre rockslope.
The main goal of this project is to investigate the possible cause(s) of the displacements observed through radar interferometry. Several untested (working) hypotheses are suggested, they include: 1) Freezing of the rock surface; 2) Mechanical response to glacier dynamics; and 3) Hydro-mechanical response due to draining of the Gornersee. A new radar measurement campaign, using the GPRI is planned for Summer 2009 in order to observe the rock wall response over several diurnal cycles. Measurements will ideally be taken with and without the influence of lake drainage. The project also involves field mapping and photogrammetric analysis (i.e. 3G shapemetrix) of rock-mass characteristics of the target rock slope.
Download extended abstract: Download (PDF, 47 KB) (PDF, 47 KB)
Dominic Stadlin
The influence of elastic properties of brittle rocks on tunnel behaviour and design
The elastic properties of a rock mass have an important influence on the stress path
development and total deformation around an underground opening. Consequently, the choice of the elastic properties in numerical calculations influences the behaviour of the rock mass and the overall stability. Intensive research is in progress to understand to what extent the choice of the loading (deformation-), re-loading (elastic) modulus, and unloading modulus influences the prediction of rock mass behaviour and related stability issues. The item becomes more complicated when considering the influence of anisotropy, heterogeneities, confinement dependent elastic properties or interactions between parallel tunnel tubes.
Download extended abstract: Download (PDF, 11 KB) (PDF, 11 KB)