MSc Students 2016-2017
Konstantinos Bischiniotis
Characterization of thermal properties of the geothermal reservoir
Enhanced Geothermal Systems (EGS) have the potential to provide long term and CO2-emission-free contribution to the world energy inventory. The EGS concept is to extract the heat from the rock mass by circulating fluid in fractures created during stimulation and/or reactivated existing fractures. For the efficiency and longevity of an EGS system, it is critical to carefully characterize the spatial distribution of heat exchange in the aquifer. To enhance the understanding of thermohydrologic behavior of a stimulated reservoir a new 10-50 m scale Stimulation Experiment was recently executed at the Grimsel Underground Research Laboratory. The experimental design includes two high-pressure injection boreholes, and a large number (more than 10) of sub-horizontal and sub-vertical monitoring boreholes drilled into the test volume. In order to provide detailed insights about flow paths controlling heat transport in stimulated fracture network the circulation in situ test is currently planned. Hot water will be circulated between boreholes in the stimulated fracture network and the elevation of rock matrix temperature as well the temperature of water flowing through connected fractures will be monitored. With the help of discrete fracture network numerical model, collected temperature data will be then used to evaluate important reservoir parameters including swept volume, the residence time distribution, and to identify connected flow paths. The goal of this Master thesis is to investigate thermal properties of the test volume in situ using a fiber optic distributed temperature sensing (FO-DTS) technology. Having in situ estimates for thermal properties can reduce uncertainty in related numerical models.
Supervisors: Maria Klepikova, Reza Jalali, Bernard Brixel
External Supervisors: Claudio Madonna, Viola Becattini
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Timon Blöchliger
Modeling of hydro-mechanical processes in landslides: from empirical to physical based models exemplified by the Cerentino Landslide, Ticino.
The modelling of coupled hydro-mechanical processes in deep-seated landslides is a not-straightforward task. The processes involved are difficult to characterize and strongly controlled by the internal rock properties and the boundary conditions such as groundwater recharge and induced porewater pressure variations (Helmstetter et al., 2002). Most of the models used in the literature are based on statistical or simplified 1D model approaches which often imply high uncertainties for predicting mass movement. Finding efficient approaches to model such hydro-mechanical processes accounting for time dependent inputs such as transient effective groundwater recharge and evolution of rock properties (strength, hydraulic conductivity, porosity) is still an active research area.
In this master thesis, the selected student will implement and compare two different approaches for modelling the evolution of landslide movement. The two approaches will be tested and validated based on the data monitored for the Cerentino landslide, located in Ticino, for which high resolution displacement, climatic and hydrogeological data are available.
Supervisor: Clement Roques
Co-supervisors: Simon Löw, Andrea Manconi
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Maud Lise Galletti
Moosfluh: towards a rock slope failure?
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. Such a critical evolution resulted in an increased number of local rock failures and caused the generation of several deep tensile cracks, hindering the access to hiking paths visited by tourists. We expect that during the summer 2017 a significant acceleration will be observed again. During the acceleration phase, rock fall events will also take place at different locations of the landside body, and involving different volumes. The main goal of the project is to compare/correlate surface deformation and processes observed with remote sensing techniques with the occurrence, the location and the size of rockfalls in order to better characterize the kinematic evolution of a failing rock slope over space and time.
Supervisor: Andrea Manconi
Co-supervisors: Franzi Glueer, Simon Löw
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Nina Sarah Jones
Marin Andreas Kradolfer
The role of ice filled cracks on rock slope stability – a laboratory study
Project Framework:
Ice filled tension cracks are commonly observed in association with active or catastrophic rock slope failures located in potential permafrost regions of the Alps. Displacement or dislocation along cracks in many of these rock slopes has been observed to primarily occur when the crack top temperature or air temperature drops below zero in late fall to winter. Long-term temperature records from boreholes in active rock slope instabilities in permafrost regions suggest that the maximum temperature in the deeper underground occurs in late fall to winter (i.e. contemporaneous with the observed acceleration phases) due to a delayed temperature propagation into the rock mass. We suggest that the temperature gradient associated with higher temperatures in the deeper underground and sub-zero temperatures at the crack tops causes the migration of free water to the tension cracks, which then expands on freezing, causing the cracks to open. These processes are difficult to test and control on the field scale. Thus, we propose a laboratory test set-up that mimics these processes on the decimeter scale.
Supervisors: Florian Amann, Kerry Leith
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Stéphane Leresche
Carlos Jorje Pereira Soares
A deep and complete knowledge about the rock structures in an underground excavation, particularly in tunnels, is crucial for the final success of an engineering project. In fact, estimation and prediction of hazardous geological conditions, especially in front of tunnel faces, are considered one of the most critical tasks to be conducted during excavation (Alimoradi et al., 2008). Located in the Jura Mountains (NW of Switzerland), the new N2 highway tunnel Belchen (Sanierungstunnel Belchen, STB), recently being excavated with a tunnel-boring machine (TBM), cuts two large portions of Opalinus clay, fine-grained sedimentary rock designated as target formation for nuclear waste repository facilities by the National Cooperative for the Disposal of Radioactive Waste (NAGRA). As part of a long-term project aiming to characterize the behaviour of the Opalinus clay rock mass during TBM tunnelling (Ziegler and Loew, 2016), this thesis investigates tunnel face breakouts geometries and relative causative geological factors along the second Opalinus clay section (TM 973–1492). Furthermore, detailed geological characterisation of Opalinus clay structures, e.g. bedding planes, slickenside bearing discontinuities and faults, scaly clay zones, were investigated in a specific tunnel area in the surroundings of a cross-passage tunnel (CP5a) at TM 1397.
Supervisor: Martin Ziegler
Michael Rickenbacher
Moab Khotsong gold mine, South Africa: Rock strength, stress, and faulting
At the Moab Khotsong gold mine from AngloGold Ashanti at external page Orkney, south of Klerksdorp (North West Province, South Africa) a M5.5 earthquake took place on 5th August 2014. The M5.5 earthquake and its after-shocks, which are still ongoing, locate between 3.5 km and 7 km below ground surface with left-lateral strike-slip faulting mechanisms on an unknown geological structure striking NNW-SSE and dipping nearly vertically. Thus, the upper edge of the activated fault is only some hundred meters below the nearest mine workings at 3 km depth. Mining-induced alteration of the state of stress and the causes of mine seismicity in general are hot topics that warrant research in South Africa’s deep mines. Within the frame of the new ICDP project external page Drilling into seismogenic zones of M2.0 – M5.5 earthquakes in deep South African gold mines (DSeis) several long boreholes will be drilled downwards from the mining level depth at about 3 km below ground and fully cored with double- and/or triple-tube core barrels. The first deep borehole will be drilled starting end of February 2017 with current MSc student Nicolas Berset on site in South Africa.
Supervisors: Martin Ziegler, Benoît Valley (Université de Neuchâtel)
Benjamin Ruf
Characterization of erosion/deposition processes due to lahars at Volcán de Colima (Mexico) with remote sensing techniques
Volcán de Colima (hereafter VdC) is a large and active stratovolcano located in western side of Mexico. A peculiar characteristic of VdC, as observed in other active stratovolcanoes, are the occurrence of rainfall-triggered lahars, i.e. unconsolidated pyroclastic material eroded by superficial water forming dilute sediment-laden flows. These phenomena are probably the most frequent secondary hazard event at stratovolcanoes, and VdC is natural laboratory for monitoring and studying lahar processes. The main goal of this study is to use remote sensing techniques to investigate the evolution of erosion/deposition at VdC. In particular, space borne Synthetic Aperture Radar (SAR) imagery will be exploited. There are not pre-defined algorithms in literature for this case study, thus the student will have to challenge (with the help of the supervisors) the topic by developing a strategy for SAR data processing to provide (semi)quantitative information on the spatial and temporal evolution of erosion/deposition processes due to lahars. In addition, optical imagery will be acquired on site by installing a time lapse camera and performing multitemporal UAV flights at the Montegrande site. The student will be hosted for a period of about 3 months at UNAM and will participate to the installation and field activities with the local scientists.
Supervisor: Andrea Manconi
Co-supervisors (UNAM, Mexico): Velio Coviello, Lucia Capra
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Kevin Miklas Schögrunder
Monitoring and Analysis of Hydromechanical Processes in the Deep Cerentino Rockslide (Ticino)
The Cerentino slope instability, 25 km north of Locarno in Ticino, is a 50-70 million m3 creeping rock mass affecting several hamlets and important local infrastructure. Although it has been studied for over 30 years, its geological, structural, and mechanical contexts are poorly understood. Based on preliminary investigations including several deep boreholes and surface displacement monitoring, this landslide is assumed to represent a compound rockslide with a strongly curved basal rupture plane. Borehole cores from the sliding mass are strongly fractured and sheared, and it is even difficult to classify the material into soil or rock. The proposed work is part of a larger investigation of the Cerentino instability which should finally lead to the design of long stabilization measures (such as a drainage tunnel). A first MSc student is currently studying the geological and hydrogeological structure of this landslide.
Supervisors: Simon Löw, Clément Roques
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Christopher Stallard
Characterisation of core fractures and diametrical core deformation analysis of a rock core originating from the 5 km deep Basel-1 well
Characterisation of the stress state of a rock mass is an important part in the geological assessment of a project site. In the external page Basel-1 petrothermal well about 8 m core was obtained from approximately 4909 m to 4917 m depth. Borehole breakouts of high confidence were identified in this depth range from acoustic televiewer logs. The core pieces show no natural fractures. However, core damage in the form of transverse features that resemble incipient to fully-developed core disking fractures are seen along the entirety of the core. Core disking is a consequence of high borehole-perpendicular stresses, and the disking features can be used as an independent constraint on the directions and relative magnitudes of the principal stresses. Furthermore, the SHmax orientation may also be inferred from the non-circular geometry of a core's circumference caused by the differential lateral expansion of the core upon extraction from a differentially stressed rock mass.
Supervisors: Martin Ziegler, Claudio Madonna (SCCER), Keith F. Evans (Geothermal Energy and Geofluids), Benoît Valley (Centre for Hydrogeology and Geothermics, Université de Neuchâtel)
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Nina Urfer
In-situ testing of hydro-mechanical properties of fault zones
The hydro-mechanical (HM) response and properties of natural fractures and faults in response to effectives stress changes is of foremost relevance in many fields of geomechanics, and in particular for understanding and predicting the response of Enhanced Geothermal Systems. Of particular interest are the HM-coupled fault properties and changes is transmissivity with increasing/decreasing effective stress. On a laboratory-scale, considerable effort has been devoted to experiments that address the role of effective stress changes on normal fracture opening and closure, shear dilatancy and related permeability changes. These experiments have demonstrated that the relationship between fluid pressure change, fracture opening and flow within rough natural fractures are strongly non-linear. One important aspect is that the mechanical aperture am(i.e., the physical distance between two fracture surfaces) and hydraulic aperture ah (i.e., the aperture accommodating flux) are not equal in rough fractures as suggested by the absolute form of the cubic law (i.e. ah = am) for laminar flow between two smooth plates (i.e., the so-called parallel plate model). In fact, hydraulic aperture is often significantly smaller. Even though great progress has been made on understanding the HM coupled behaviour of natural fractures on the laboratory scale, it is not clear how these results can be up-scaled to the reservoir scale. In-situ experiments at the intermediate-scale (i.e., decameter-scale) can serve as a bridge between laboratory and reservoir scales and contribute to an improved understanding of reservoir behaviour during stimulation, and to enable up-scaling of hydro-mechanical information. Unfortunately only few very well controlled and heavily instrumented studies have been performed on the intermediate scale so far.
Within the In-Situ Stimulation and Circulation (ISC) experiment at the Grimsel Test Site (GTS) we have the unique possibility to perform HM-coupled in-situ experiments in 4 boreholes that have been drilled and completed to monitor both the pore pressure response in open intervals across fractures/faults and associated normal displacements using distributed fibre optics cable. These boreholes can be used to perform a series of tests that allow quantifying some relevant HM coupled fault properties.
Supervisors: Florian Amann, Reza Jalali, Valentin Gischig
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Andrina Vlasek
Deep Structures of Large Toppling Slopes
Many phenomena of toppling landslides have been described in the literature based on observations on ground surface, especially in road cuts and open-pit mines (e.g. Goodman and Bray, 1976). In addition many researchers have studied toppling conditions with analytical (e.g. Smith 2015) and numerical models (e.g. Nichol et al 2002), and compared them with near-surface structural observations.
However, many alpine mountain slopes show deep (>100 m) toppling phenomena, as documented mainly in unpublished underground excavation reports from tunnels, underground pipelines and hydropower drifts (e.g. Keller and Schneider 1982; Klemenz 1974). Also many GSGSD (deep seated gravitational slope deformations) in the Alps show toppling phenomena. For all these cases, ground surface observations of phenomena and displacements are not sufficient to fully understand toppling structures and kinematics at larger and deeper scale. This projects aims at improving our understanding of deep structures, kinematics and movements in large toppling slopes.
Supervisors: Simon Löw (Main Supervision), Franziska Glüer