MSc Students 2018-2019
Brian Antonioli
Analysis of the impact of suction pressure, rock structure, and test setup on the mode II fracture toughness of Opalinus Clay Shale (PF Experiment, Mont Terri Project)
The goal of this project is to determine the effect of rock structure and suction pressure on Opalinus Clay mode II fracture toughness. The study aims at increasing our understanding of Opalinus Clay fracture mechanical properties, which are relevant for the long-term disposal of radioactive waste.
The successful candidate will conduct mode II fracture toughness tests on Opalinus Clay core specimen from the new Belchen highway tunnel and from the Mont Terri underground laboratory. Different loading directions with respect to anisotropy planes, e.g., parallel, perpendicular, and inclined to bedding planes, and specimen with different degree of saturation (suction pressure) will be tested. We can conduct a PTS/CP test in a triaxial setup as shown in Fig. 1b using a cylindrical, notched Opalinus Clay specimen or in a biaxial setup using a notched, prismatic specimen. The latter may allow for observing the fracture formation and analysing displacements using Digital Image Correlation (DIC) technique on photographs recorded with highspeed cameras during the experiment. Besides the PTS/CP-tests that allow for confinement control, laterally unconfined setups will be tested (e.g., three-point bending semi disc with oblique notch and/or centrally cracked Brazilian disc; e.g., Backers, 2004) to explore the impact of sample shape and setup (confined and unconfined) on FT mode II. The fracture process may be monitored acoustically. Optionally, the morphology of the resulting fracture surfaces will be characterised after testing, e.g. with photogrammetric scans.
Supervisors: Dr. Martin Ziegler, Dr. Omid Moradian, Nathan Dutler (Université de Neuchâtel)
Kwabena Atobra
Fluid Injection and Fault Reactivation in Enhanced Geothermal Systems (EGS) in Crystalline Rocks
The geothermal power generation with Enhanced Geothermal Systems (EGS) is one of the proposed renewable sources of energy for Switzerland. The technique involves three mechanisms 1) hydraulic fracturing, 2) hydraulic shearing along faults and natural fractures, and 3) a combination of hydraulic fracturing and hydraulic shearing in which the hydraulic fracture initiates and propagates first and then it activates the faults and the natural fractures. Despite considerable advancement in this area, the goal of sufficiently enhancing permeability has not yet been obtained in a sustained way and fracture induced seismicity sometimes obstructs the EGS projects (e.g. in Basel and St. Gallen).
In this MSc research, the second mechanism (hydraulic shearing) will be investigated experimentally and also numerically (depending on the time and interest of the candidate). We are going to conduct an experimental investigation on sliding fault activations and assess the effect of different fluid pressurization paths (monotonic, cyclic, progressive) on fault slip and associated induced seismicity in crystalline rocks. Both bare fault surfaces and gouged faults will be tested. We will develop a seismic–controlled injection path in which the seismicity stays lower than a predefined threshold as “traffic-light” system to stop large earthquakes from happening (Deichmann and Giardini, 2009, Ellsworth, 2013).
By conducting this research, we hope to be able to answer the following questions:
1.) How does shear reactivation of bare faults differ from gouged faults?
2.) Is fault reactivation under fluid injection in crystalline rocks seismic or aseismic? How do seismic signals change prior to fault slip? Can we predict the main-shock by the seismic precursors?
3.) How do different fluid injection paths affect the rate and magnitude of the induced earthquake? What is the optimal injection path?
4.) How do source locations and focal mechanisms (shear, tensile, mixed) of the seismic signals change under different fluid injection paths?
5.) What is the upper-limit of the magnitude-detection threshold in which the failure is controllable?
Supervisor: Dr. Omid Moradian
Michele Bernasconi
Progressive failure around a large-diameter borehole simulating structurally- controlled tunnel overbreaks in Opalinus Clay Shale (PF Experiment, Mont Terri URL)
The goal of this MSc project is to investigate the spatial and temporal evolution of damage (i.e., overbreaks) of a large diameter borehole that simulates a repository tunnel cut by a steep fault or fracture zone (Fig. 2). The experiment will be conducted at the MT URL. Borehole failure will be monitored by means of a photogrammetric unit that repetitively records the inner geometry of the environmentally-controlled borehole in 360°. Photogrammetry allows to calculate the radial extents and locations of borehole overbreaks, and at the same time allows to qualitatively investigate the fractures that led to the collapse. The thesis will focus on the investigation of the visible evolution of the borehole overbreak. The results will be discussed and interpreted within a broader perspective (rock mass heterogeneity, state of saturation, stress around the fault/fracture zone, etc.). A set of monitoring boreholes around the large-diameter experiment borehole will also be installed and will provide a broad range of rock mass properties and their changes during progressive failure and overbreak (note the analyses of these datasets are not part of the MSc thesis). Structural data from monitoring boreholes, i.e., core and borehole logs, will be used in the MSc thesis to constrain the rock mass structures of the experiment.
Supervisors: Dr. Martin Ziegler, Tobias Renz
Thierry Krummenacher
Hydrogeological Analysis of an Active Soil Landslide
Earthflows are a type of landslide that occur in plastic soils. These phenomena are characterized by periodic surges, which reach velocities of meters/day to meters/week. Due to these significant displacements, earthflows can rupture pipelines, damage roads and buildings, and are costly to remediate. Understanding the mechanisms that control the motion of these events is important to manage the risk they pose. Displacement in earthflows occurs primarily along discrete shear surfaces within the landslide mass, and landslide motion can be triggered by rising pore-pressures on these surfaces. This pore pressure rise is often caused by rainfall and/or snowmelt infiltrating into the unsaturated landslide body. Due to the dynamics of unsaturated infiltration, there can be a delay between precipitation and motion, which has significant implications for understanding the mechanisms acting in earthflows. In this project, the student will create a detailed hydrogeological model of the Schlucher Landslide, an active earthflow located in Liechtenstein. The student will use both 1-D and 2-D infiltration modelling to understand the dynamics of pore pressure rise in the landslide, and use this information to study the mechanisms that govern motion of this active earthflow.
Supervisors: Dr. Jordan Aaron, Prof. Simon Löw
Selina Lüchinger
Time-dependent changes in permeability of excavation damaged zones at the Mont Terri Underground Rock Laboratory (MT URL)
The goal of this thesis is to assess how the permeability of the EDZ has evolved over 20 years using pneumatic (i.e., air/gas) testing, and to evaluate what rock and rock mass properties might have influenced these changes. Permeability measurements have not been repeated in boreholes over such long time scales, and not without changes to the state of the EDZ (cf., water injection during hydrau-lic testing). Thus, our experiment aims at understanding the natural ability of the Opalinus Clay to self-seal and what its impact is on permeability over longer time scales than previously studied. The integration of the pneumatic tests with geophysical borehole logging and structural borehole and core mapping will help give a more holistic view of how the EDZ has changed over 20 years. Additionally, laboratory tests conducted on extracted core and fracture material will be used to understand how certain properties (e.g., porosity, water content, fracture mineralization and geometry, etc) influence permeability changes.
The first work in this project will be to carry out drilling of radial boreholes in Gallery 98 in a similar orientation as previous tests in 1999. Once drilling is completed, we will conduct pneumatic tests in the boreholes. It is likely that pneumatic testing and geophysical logging will be carried out by our project partner BGR. Pneumatic tests typically involve either air extraction or nitrogen injection into chosen intervals with-in a borehole. Air and gas flow rates are then monitored and converted to a permeability value. Cores taken from the boreholes will be mapped and logged with geophysical tools (e.g., ERT, seismics). Structural analysis of the fracture network, through drillcore mapping and optical televiewer (OPTV) interpretation, around the experimental site will be a key component of this work. The interested M.Sc. student will help support the drilling activities and pneumatic tests, map the cores, interpret borehole logs, and analyze the results of the pneumatic testing. Thus, the student will work with a broad range of data sets and complete field work partly in the MT URL. Systematic laboratory tests might also be carried out on some of the extracted borehole cores in order to understand which rock mass properties could have influenced our results. Such tests could include systematic water content and porosity measurements.
Supervisors: Molly Williams, Dr. Martin Ziegler, Dr. Hua Shao (BGR, to be confirmed)
Fiona Nägeli
Impact of saturation state, anisotropy, and composition on micromechanical properties of fractured Opalinus Clay shale
Rock fractures around nuclear waste repository drifts, such as fractures formed during excavation works, may undergo mineralogical, structural, and mechanical changes after waste emplacement. The properties of these fractures and the states of their environment are important to understand expected fracture closure, i.e., whether fracture sealing occurs and if what sealing processes will act. In order to investigate if mechanical properties, such as the stiffness, of fractures in the Excavation Damage Zone (EDZ) have changed since EDZ formation this work investigates the micromechanical properties of recent and up to 20 years old EDZ fractures of the Mont Terri URL. The deformation and strength of Opalinus Clay shale depends not only on its mineralogical composition and consolidation state but also on its saturation state. Thus, tests will be conducted under controlled humidity conditions. The work will be carried out in the frame of the Mont Terri SE-P (SElf-Sealing Processes) project and in collaboration with the Material Science and Technology research institute EMPA in Thun.
Supervisors: Dr. Martin Ziegler, TBD
Presty Paulose
Mapping and numerical modelling of flash flood hazard in the Valley of the Kings (Luxor, Egypt)
The Valley of the Kings is a popular tourist destination located near Luxor, Egypt. This area was used as a burial place for royals and nobles, and contains over 60 tombs. Flash flood deposits have been noted on the valley floor, and within some of the tombs. The aim of this Master’s thesis is to investigate the flash flood hazard in the Valley of the Kings. Mapping of existing deposits will be carried out using a high-resolution LiDAR model of the valley. Numerical modelling will be used to assess the potential inundation areas of future flash floods.
Supervisors: Jordan Aaron and Martin Ziegler
Valentina Piccirilli
Field Investigation and Back-Analysis of the Diablerets Rock Avalanches
Rock avalanches are large volume flows of fragmented rock. They are a significant hazard worldwide, however quantifying the hazard posed by these events is challenging. One major uncertainty in such hazard analysis is prediction of the impact area and velocity of the event before it occurs. The difficulty in predicting these quantities is partially due to a lack of understanding of the movement mechanisms governing rock avalanche motion. The Diablerets Rock Avalanches which occurred in 1714 and 1749 provide a unique opportunity to investigate the mechanisms governing rock avalanche motion. Due to the unique history of this site, it provides an opportunity to study the interaction of flowing rock avalanche debris with path material. This master’s project will combine field and laboratory investigations with numerical modelling in order to gain insight into the mechanisms controlling the motion of these two rock avalanches.
Supervisors: Dr. Jordan Aaron and Dr. Fabio de Blasio (University of Milano-Bicocca)
Ivo Stirnimann
Relationship between slope deformation and rock failure events at Moosfluh
The slow, long-term evolution of rock slopes is punctuated by failures producing rapid mass wasting. However, the spatial and temporal relationships governing the progressive development of rock slope movements towards failure are still poorly understood. Slope movements associated to deep-seated rock slope instabilities occur throughout the Alps and range generally from 1 to 10 cm/year (Crosta et al., 2013). At some locations, the surface displacements suddenly increase to higher values and the rock mass starts to degrade, tensile fractures form and the frequency of rock fall activity increases (Petley, 2004). A deep-seated slope instability located in the vicinity of the Great Aletsch glacier, in the area called “Moosfluh”, has shown during the past 20 years evidences of a slow but progressive increase of surface displacement. In the late summer 2016, an unusual acceleration of the Moosfluh rockslide was observed. Compared to previous years, when ground deformations were in the order of few centimeters, in the period September-October 2016 maximum velocities have reached locally ~1 m/day. The main goal of this project is to investigate spatial and temporal correlations between surface displacement and rock slope failures at the scale of the Moosfluh slope. During the acceleration phase, rock fall events take place at different locations of the landside body, and involve different volumes. We aim at comparing/correlating surface deformation and processes observed with ground based remote sensing techniques with the occurrence, the location and the size of rock failure in order to better characterize the kinematic evolution of a failing rock slope over space and time.
Supervisors: Dr. Andrea Manconi, Valentin Bickel, and Prof. Simon Löw
Björn Bauhofer
Exploring the Controlling Factors on River Baseflow Recession Worldwide
Glaciers, snowpack and groundwater are the main contributors to stream water during dry periods. Typically, two distinct stream regimes are commonly observed: 1) the surface-flow dominated systems, with flashy streamflow regimes, rapid base flow recession and very low summer flows; and 2) the spring-fed watersheds, with a slow-responding streamflow regime, and a long and sustained base flow recession that maintains late summer streamflow through deep-groundwater contributions to high volume springs. Although the characterization of groundwater – surface water (GW-SW) interaction is critically needed for water resource management purposes, the factors that control their dynamics at base flow remain poorly understood.
Hydrograph recession analysis during base flow regimes provides unique opportunities to test hypotheses on how groundwater systems behave in dry conditions. Current theories established to interpret recession curves generally assume idealized homogeneous groundwater reservoirs. The role of structural heterogeneities is not taken into account and remains unresolved. The aim of this master thesis is to test current GW-SW hypothesis by performing river recession analysis in mountain regions worldwide and quantify how results deviate from established theories. The results will be analyzed in a statistical framework (correlation – Principal Component Analysis) in order to identify the main factors that might control transient recession behaviors. The student will base his/her analysis on regions with different geomorphological and geological contexts for which discharge time series are available. Specifically, the student will 1) compile hydrological and geological data available for different regions through existing databases (Bafu, USGS, BRGM…), 2) perform analysis of discharge time series using the well-known method established by Brutsaert and Nieber (Brutsaert and Niebert 1977, Roques et al. 2017) in order to identify different recession parameters, 3) identify the main geological and geomorphological signatures for each system that can influence such behaviors. Numerical modelling will also be used in order to validate main hypotheses identified.
Supervisors: Clément Roques and Kerry Leith
Matthias Meier
Development of New Flow Logging Methodologies and Data Analysis approach for Hydraulic Characterization of the Bedretto Underground Laboratory (BUL)
ETH is currently constructing an underground research laboratory in the Bedretto Adit of the Furka Base Tunnel (BUL) within the framework of a multi-disciplinary collaboration of the Swiss Competence Center for Supply of Energy. The first large scale experiments carried out in this lab are related to enhanced geothermal systems, and will include drilling of a large number of long (250-300m) injection and monitoring boreholes. A hydrogeological model of the test volume is a fundamental component of this multi-disciplinary project and will be developed from a combination of measurements carried out during the drilling operations, and during a special characterization phase following the drilling phase.
This thesis will mainly focus on the analysis of hydraulic data collected by the drilling crew during borehole drilling in 2019 (Figure 3). This data set includes locations and hydraulic properties of preferential groundwater inflows to the subsurface boreholes, and cross-hole hydraulic interactions monitored in packed-off intervals of completed boreholes in response to the during drilling of subsequent boreholes (Figure 4). The testing protocol applied will follow the operations designed for pre-drillings the Lötschberg and Gotthard Base Tunnels (Masset and Loew 2013, Pesendorfer and Loew 2007, 2010). The field data will be interpreted with analytical models used in transient pressure test analysis. The hydrogeological interpretations will by compared with structural geology interpretations from a companion MSc thesis (David Jordan) and geophysical borehole investigations. According to the current planning, the main data sets of projects will be collected in the second half of 2019.
The following tasks are required to be carried out in this thesis:
- Mapping and characterization of discontinuities (brittle faults, ductile shear zones, mesoscale fractures, foliations) of new drill cores from the Rotondo granite in BUL
- Comparison of geological structures with geophysical borehole surveys
- Interactions with drilling crew during inflow logging and pressure build-up operations. Data collection and quality control
- On-site support during heat dilution test
- On-site support during resistivity contrast test
- Analysis of borehole flow logging results using analytical/numerical (Comsol/Fracman) solutions in order to improve the available geological model of the system.
Supervisors: Prof. Simon Loew, Dr. Nima Gholizadeh
Andri Münger
Characterisation of Preferential Groundwater and Heat Transport Pathways of Test Volume at the Bedretto Underground Laboratory (BUL)
ETH is currently constructing an underground research laboratory in the Bedretto Adit of the Furka Base Tunnel (BUL) within the framework of a multi-disciplinary collaboration of the Swiss Competence Center for Supply of Energy. The first large scale experiments carried out in this lab are related to enhanced geothermal systems, and will include drilling of a large number of long (250-300m) injection and monitoring boreholes. A hydrogeological model of the test volume is a fundamental component of this multi-disciplinary project and will be developed from a combination of measurements carried out during the drilling operations, and during a special characterization phase following the drilling phase.
This thesis will mainly focus on the execution and analysis of the hydrogeological testing program following the drilling phase. This testing program includes single and cross-hole packer testing, and cross-well tracer tests with dyes. According to the current planning, the main data sets of projects will be collected in the second half of 2019.
The following tasks are required to be carried out in this thesis:
- Comparison of geological structures with geophysical borehole surveys
- On-site support during dye tracer testing operations
- On-site support during single and cross hole packer testing operations
- Analysis of single-hole transient pressure or flow responses with analytical solutions
- Analysis of hydraulic cross-hole and fracture network responses, possibly with a discrete fracture network model (Fracman/Mafic).
Isabel Kaspers
Geological and geomorphological control on the distribution of groundwater flow and residence times in an Alpine watershed
The study of groundwater flow partitioning and residence time distribution in watersheds have been subjects of extensive research activities. Most of these studies consider that topography has a first-order control over these parameters. However, similarly to what is observed at small scales, structural heterogeneity of the aquifer system (lithological variations, geological discontinuities, spatial distribution of topographic and tectonic stresses) might have a significant control into the distribution of flow paths. To what degree aquifer heterogeneity plays a critical role remains poorly understood. This master thesis will specifically investigate the respective roles played by topography and geological heterogeneity in the control on flow paths and residence times distributions using a mechanistic numerical modeling approach (Alp Canfinal watershed, Poschiavo).
Supervisors: Dr. Clément Roques (ETHZ), Dr. Sarah Leray (Pontifical Catholic University of Chile), Dr. Kerry Leith (ETHZ) and Prof. Simon Loew (ETHZ)