MSc Students 2009-2010
David Büsser
Groundwater Recharge Induced Rockslope Deformations in Alpine Valleys, Switzerland
In order to detect possible ground surface deformations during the construction phase of the Gotthard Base Tunnel in central Switzerland, a high-precision automatic geodetic monitoring network has been installed above the tunnel trajectory. This geodetic monitoring network consists of several local networks, composed of total stations and reflectors that are located along six cross-sections in 3 alpine valleys (Val Curnera, Val Nalps, Val Termine/Santa Maria). Measurements have been initiated several years before the tunnelling excavation started. During this period natural ground surface motions and strains between reflector pairs in these sections could be recorded. The underlying mechanisms are annual changes in groundwater table elevation in response to snow melt and summer rainstorms, leading to pore pressure changes and elastic rock mass deformations (Loew et al. 2007). The monitoring stations at these 6 cross-sections show significant differences in the amount of annual reversible deformations. This MSc thesis shall contribute towards an improved understanding of the factors responsible for the differences in rock mass deformation at the various study sites. The MSc study includes substantial field work (mapping of hydrogeological features, soil cover and rock mass properties at the monitoring sections), possibly technical installations and operations (climate stations), and variable amounts of computer based data processing and modeling (depending on interest).
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Jocelyn Gisiger
Examination of the shallow subsurface temperature distribution in Zürich
The focus of this thesis is set on regional anthropogenic effects of geothermal energy use and waste heat injection in the shallow geological underground of Zürich. In the big cities of Europe, North America and Asia meanwhile serious artificial temperature anomalies evolve in the underlying aquifers. Also the geothermal energy use in the area of Zürich is intense. Has this also generated such “subsurface climate change”? This will be subject to this thesis.
The work will cover collection of available studies, raw data material and reports on spatially and temporally resolved temperature measurements of the area of Zürich city. Additionally, field temperature measurements will be conducted at selected pumping and observation wells. The heterogeneous data sets will be filtered and categorized with respect to measurement dates, depths and accuracy. Finally a 3D isotherm map will be developed and discussed with respect to the role of geothermal energy use.
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Lukas Hamann
Geological-geotechnical analysis of the Vicosoprano rock fall events
South of Vicosporano (Grison, Switzerland), a small portion of the La Fiamma north face failed in 1990 catastrophically and unexpectedly. Geological inspection of the release area revealed ongoing disintegration of the rock mass, and subsequent collapses were anticipated. In order to assess future instability development, an early warning system was installed in 1991 utilizing an automatic total station at Vicosoprano and multiple optical prisms within the unstable rock mass. In summer 2002, two consecutive catastrophic events occurred releasing an estimated total volume of 50’000 m3. Because of the monitoring system it was possible to identify critical accelerations prior to the event, and parts of the village were evacuated. Monitoring of the remaining unstable rock mass is ongoing, and 19 years of displacement data are available to date.
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Michael Hunziker
Earthquake-Induced Rock Slope Failures: The 1946 Rawilhorn Rock Avalanche
Landslides accompany almost all major earthquakes striking steep terrain and are among the most destructive secondary effects of shaking. The last major earthquake in Switzerland (1946 Sierre, M≈6.1) triggered a number of small landslides within the epicentral region. Four months later, however, an M≈6.0 aftershock induced a very large rock avalanche from the steep slopes of the Rawilhorn; one of the few landslides in the Swiss Alps known to have been directly triggered by seismic shaking. The rock avalanche released 4-5 million m3 of rock from a ridge approximately 600 m high. This research aims to: (1) construct a geological model and determine the failure mode of the Rawilhorn rock avalanche, (2) assess the influence of repeated seismic loading on rock mass strength degradation and slope stability, and (3) determine the influence of other contributing environmental and seismological variables (e.g. snow melt, earthquake frequency content) in leading to the rock avalanche.
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Andreas Ludwig
Kinematic Analysis of a Complex Rockslide - The Example of Brienz, Graubünden
Matthias Meyer
Investigation of the recharge area of the important Bodmi Spring near Flüelen, Canton Uri
The Bodmi springs have a flow rate of 50 l/s (3000 l/min) at a height of 880 m (a.S.L.) and originate from above the village of Flüelen to the left side of the Gruonbach valley. The high yield of this spring emerged after a blow out through the confining layer in 1999 after a strong rainfall. Since this spring origin is situated about 300 m above the village of Flüelen, the spring water is first conducted into a turbine which yields about 600’000 KWh per year and thereafter used for the drinking water supply of the village.
The aim of this investigation is i) to characterize the chemical and isotopic properties of this spring water, and ii) to characterize the hydrogeological flow systems within the context of regional and local geology and tectonics. In order to determine distinct flow paths experiments with fluorescence tracer will be necessary. The work will be carried out in close collaboration with the consulting geologist and the village authorities of Flüelen. Tracer tests and chemical constituents will be analyzed in the hydrochemical lab of engineering Geology.
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Philippe Moes
Climatic Controls on Paraglacial Rock Mass Weathering
Glacial erosion deepens valley floors and steepens adjacent rock slopes. With glacier retreat, these slopes are exposed in a meta-stable state and prone to rapid strength degradation and collapse. Rockwalls recently exposed to the atmosphere are beset by a suite of physical and chemical processes known as exogenic weathering factors. Examples include mechanical weathering by ice, thermo-elastic stresses, and chemical weathering related to fluid infiltration. This project aims to investigate time-dependent weathering of recently deglaciated rockwalls by exogenic mechanisms. Rock slope surfaces exposed at different times since the Last Glacial Maximum will be investigated and compared. Rock mass strength parameters will be quantified and key varying properties noted. Field evidence will guide us to suggest mechanisms of rock mass breakdown by physical or chemical weathering, and constrain weathering rates. The impact of rock mass strength degradation by paraglacial weathering will be considered for the development of Alpine rock slope instabilities.
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Sarah Nussbaumer
Seasonal effect on rock instability - Case of Moosfluhe - Sperihorn rock instability (Aletschglacier VS)
Susanne Scheiwiller
Impacts of Climate Change and Contamination on Springs
The goal of this Master Thesis is to analyze historical instrumental records on spring-water monitoring, for a possible response to climate forcing and climate change. Historical data may go back some decades. Springs will be studied, whose data will partly have to be digitized. Time series analyses and other statistical methods will be employed in both the time domain and the frequency domain, to yield insight into the discharge behavior of an individual spring. The statistical analysis can be made with the help of Eawag expertise, mainly with MATLAB functions. The springs are expected to be contaminated, therefore, concentration time series give additional information about the flow system. Mapping the catchment combined with tracer analyses (e.g., 3H/3He) as well as water chemical analyses (analyses performed by professionals) at Eawag will complement the study with field work.
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