Federal Office of Topography Swisstopo

Wabern, Switzerland

Federal Office of Topography Swisstopo

Wabern, Switzerland
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Bossart P.,Federal Office of Topography swisstopo
Swiss Journal of Geosciences | Year: 2017

The 20 papers in this Special Issue address questions related to the safe deep geological disposal of radioactive waste. Here we summarize the main results of these papers related to issues such as: formation of the excavation damaged zone, self-sealing processes, thermo-hydro-mechanical processes, anaerobic corrosion, hydrogen production and effects of microbial activity, and transport and retention processes of radionuclides. In addition, we clarify the question of transferability of results to other sites and programs and the role of rock laboratories for cooperation and training. Finally, we address the important role of the Mont Terri rock laboratory for the public acceptance of radioactive waste disposal. © 2017, Swiss Geological Society.

Schuster K.,Federal Institute for Geosciences and Natural Resources | Amann F.,ETH Zurich | Yong S.,ETH Zurich | Yong S.,Knight Piesold Ltd. | And 2 more authors.
Swiss Journal of Geosciences | Year: 2017

We present several mini-seismic methods developed and applied in recent years in the Mont Terri rock laboratory. All these applications aimed at correlating and interpreting seismically derived parameters with relevant rock-mechanical parameters and findings. The complexity of the local site setting always required very high spatial and parameter resolution. Both, seismic P- and S-wave velocities and dynamic elastic parameters, such as the dynamic Poisson’s ratio υdyn and the Young’s modulus Edyn, are used to characterise the Opalinus Clay under real in situ conditions. We were able to establish a correlation between static and dynamic elastic Young’s moduli. We describe the extremely large, small-scale variability of seismic parameters normal and parallel to the bedding plane orientation and address the question of fracture detection. We also present examples of the characterization of excavation-damaged zones with seismic parameters, including extent as well as degree of damage, and compare these to geological and structural mapping. The evolution of borehole-disturbed zones (BdZ) was deduced from repeating high-resolution borehole measurements. Finally, we quantify seismic anisotropy at dimensions between several cm and tens of m. © 2017 The Author(s)

Yong S.,Knight Piesold Ltd. | Loew S.,ETH Zurich | Schuster K.,Federal Institute for Geosciences and Natural Resources | Nussbaum C.,Federal Office of Topography swisstopo | Fidelibus C.,University of Bari
Rock Mechanics and Rock Engineering | Year: 2017

In Switzerland, the Opalinus Clay is under consideration as a potential host rock for deep geological storage of nuclear waste. The Swiss concept involves high-level waste containers emplaced in small-diameter drifts of roughly 3 m. At the Mont Terri Underground Rock Laboratory, a short mine-by experiment (EZ-B) was executed in 2005 with the objective of characterising the excavation-induced damage through an interpretation of integrated field data. The damage zone was found to consist of two parts. Fracture mapping from drillcores and televiewer images revealed a thin inner zone of macroscopic fracturing (20 cm) and devoid of borehole instabilities as well as coinciding with the lowest P-wave characteristics (normalised amplitudes and velocities). The outer zone (50–80 cm) was defined by increasing P-wave characteristics and evidence of borehole instabilities. Supplementing the data interpretation, a simplified numerical elastic stress analysis indicated that the rock mass in the sidewalls and upper western haunch are the most susceptible to spalling. In these regions, stress levels only just reach a spalling limit around 0.05 in the inner fractured zone, suggesting that the zone of macro-fracturing around the niche is not significant. It is postulated that the physical manifestation of the relatively weak bedding plane strength is dominated by bedding-perpendicular displacement as opposed to bedding-parallel shear. © 2017 Springer-Verlag Wien

Kupferschmied N.,ETH Zurich | Wild K.M.,ETH Zurich | Amann F.,ETH Zurich | Nussbaum C.,Federal Office of Topography Swisstopo | And 2 more authors.
International Journal of Rock Mechanics and Mining Sciences | Year: 2015

Opalinus Clay, a Mesozoic clay shale, has been chosen as host rock formation for the disposal of radioactive waste in Switzerland. For this study, borehole damage zones were utilized as a proxy for an excavation damage zone that forms around a circular, mechanically excavated tunnel in intact Opalinus Clay. Pilot boreholes were resin-impregnated and over-cored at different times after drilling, to provide insight into the time-dependent formation of fractures on both the micro- and the macro-scale. Observed fractures were characterized in terms of failure mode, their relation to the rock anisotropy, and the in-situ stress tensor. The analyses show that fractures that form in the short term initiate as shear fractures at the pilot-borehole wall and propagate parallel to bedding. Typically, a dominant shear fracture tangential to the pilot borehole wall was observed. Upon propagation of these shear fractures, wing cracks, horsetail splays and second-order shears form sub-parallel and sub-perpendicular to bedding planes, forming a complex fracture network, which extends a quarter pilot-borehole diameter into the rock mass. In the longer term, tangential shear fractures tend to propagate in a direction opposite to the initial propagation direction. In addition, new bedding-parallel fractures deeper in the rock develop, leading to the formation of thin slabs, buckling of the slabs when unsupported and eventually progression of the buckling zone deeper into the rock mass. Buckling is associated with the formation of extensional fractures normal to bedding in the center and lateral to the buckling zone. The zone of buckled rock slabs was found to have an extension of more than one borehole diameter at the time of preservation with resin. In the short term, the axis connecting the maximum failure depth on opposing sides of the borehole is parallel to the minimum stress direction in a plane normal to the borehole axis. In the long term, this axis rotates significantly towards the maximum stress direction, primarily as a consequence of tangential shear fracture propagation, slab formation and buckling. Dissipation of excess pore pressures may be the key process underpinning longer-term fracture propagation and formation. © 2015 Elsevier Ltd.

Ziefle G.,Federal Institute for Geosciences and Natural Resources | Matray J.-M.,Institute for Radiological Protection and Nuclear Safety | Massmann J.,Federal Institute for Geosciences and Natural Resources | Mori A.,Federal Office of Topography Swisstopo
Swiss Journal of Geosciences | Year: 2017

This paper focuses on hydraulic-mechanical effects in the Mont Terri rock laboratory (Switzerland) and investigates their impact on pore pressure, the convergence of a niche and the evolution of pre-existing cracks in the wallrock of the niche. A comparison of measurements with numerical simulation results is conducted. The presented in situ measurements include long-term data on temperature, relative humidity, and niche convergence, as well as crackmeter and jointmeter measurements determining the aperture of a bedding-parallel crack. Furthermore, time-domain-reflectometry measurements were carried out in a borehole located in the niche wall close to the crack. They provide information on the water content of the claystone. The numerical simulation is carried out with OpenGeoSys. It contains a 2-dimensional coupled hydraulic-mechanical model considering orthotropy, swelling and shrinkage effects, linear elastic material behaviour and an excavation damaged zone characterized by a zone of lower rock strength. An additional focus is laid on the evolution of cracks in the wallrock of the niche. The presented model approach allows a prediction of the temporal evolution of a desaturated zone incorporating a seasonally influenced part. The comparison with measured water contents yields good agreement. Simulation results and measurements consistently predict a convergence of the niche. The evolution of the crack aperture is influenced by long-term as well as seasonallyinfluenced effects. Due to the convergence of the niche, the long-term trend is characterized by closure of the crack. Furthermore, the seasonally influenced desaturation in winter results in opening of the crack, while the resaturation in the warm and wet summer months leads to closure of the crack. Finally, the comparison of simulation results with measurements indicates qualitative agreement. As a matter of fact, the numerical model seems to represent significant effects concerning the evolution of the crack aperture of a single crack. © 2017 The Author(s)

Nussbaum C.,Federal Office of Topography swisstopo | Bossart P.,Federal Office of Topography swisstopo | Amann F.,ETH Zurich | Aubourg C.,University of Pau and Pays de l'Adour
Swiss Journal of Geosciences | Year: 2011

Excavated in the Opalinus Clay formation, the Mont Terri underground rock laboratory in the Jura Mountains of NW Switzerland is an important international test site for researching argillaceous formations, particularly in the context of deep geological disposal of radioactive waste. The rock laboratory is intersected by naturally formed tectonic structures, as well as artificial fractures primarily formed as a consequence of tunnel excavation and the associated stress redistribution. The description and characterisation of tectonic and artificial structures is, in many cases, of key importance for interpreting the results of the various in situ experiments conducted in the rock laboratory. Systematic small-scale mapping of the tunnel walls and floor, and adjacent niches, provides basic information about the geometry and the kinematics of the geological fractures intersecting the underground laboratory. A compilation of all tectonic structures identified is presented in this paper. The underground laboratory is located in the backlimb of the Mont Terri anticline, a NNW-vergent imbricate fault-bend fold, which is characterised by a pronounced along-strike asymmetry resulting from variously oriented inherited faults. The total shortening accommodated by this structure was estimated by mass (area) balancing to be approximately 2. 1 km. The Mont Terri area is significantly affected by N- to NNE-striking normal faults of the Eo-Oligocene Rhine-Bresse transfer zone and by ENE-striking faults of Late Variscan age. Depending on their orientation with respect to the transport direction towards the NNW, these faults served as oblique and frontal ramps during the subsequent Jura thrusting in the Late Miocene. The various fault systems identified in the underground rock laboratory clearly correlate with the regional-scale structures. In addition to classical structural analysis, the anisotropy of magnetic susceptibility was measured to determine the magnetic fabric and strain imprint of the Opalinus Clay. Results indicate a well developed magnetic fabric with a magnetic foliation close to the bedding, and with two distinct magnetic lineations which are probably related to the Mont Terri anticline folding and layer-parallel shortening prior to the folding. Strain imprint is more pronounced in the overturned forelimb, which is consistent with the structural data. © 2011 Swiss Geological Society.

Climate and land use effects on forest cover in the Bernese Alps during the 20th century In this study changes in the forest cover in the municipality of Grindelwald between 1899 and 2005 was analyzed. The aim was to identify whether global warming has an effect on forest cover on a regional scale in an intensely used alpine landscape.By comparing the area of forest mapped on the Siegfried map of 1899 with the current forest using ArcGIS, positive andnegativechanges could be detected and geo-referenced. In the forest borderline ecotone, which would be sensitive to climate change, an increase of 210 ha and a decrease of 201 ha was measured. This corresponds to approximately 10% of the forestcover in Grindelwald. The balanced change in cover indicates that the forest borderline ecotone did not change very strongly during the 20th century. This can be explained by the intensive alpine agriculture of the region above the treeline. The alpine farmers tend mountain pastures by clearing saplings. Only a single large increase (46 ha) in front ofthe retreating Upper Grindelwald glacier can be attributed to global warming. Other smaller increases occurred where agricultural land has been abandoned, mostly below the 1899 tree line and thus not attributable to climate change. Decreases in forest cover can be attributed to human influences, such as expansion of alpine agriculture and tourism (construction of transportation infrastructure) and morphodynamic processes, such as avalanches. It can be concluded that forest cover in Grindelwald is strongly affected by humans. Any changes, therefore, cannot be used as a general indicator for (or against) climate change. © Author(s) 2012. This work is distributed.

Lutz S.,Federal Office of Topography swisstopo | Beutler G.,University of Bern | Schaer S.,Federal Office of Topography swisstopo | Dach R.,University of Bern | Jaggi A.,University of Bern
GPS Solutions | Year: 2014

The International GNSS Service (IGS) issues four sets of so-called ultra-rapid products per day, which are based on the contributions of the IGS Analysis Centers. The traditional (“old”) ultra-rapid orbit and earth rotation parameters (ERP) solution of the Center for Orbit Determination in Europe (CODE) was based on the output of three consecutive 3-day long-arc rapid solutions. Information from the IERS Bulletin A was required to generate the predicted part of the old CODE ultra-rapid product. The current (“new”) product, activated in November 2013, is based on the output of exactly one multi-day solution. A priori information from the IERS Bulletin A is no longer required for generating and predicting the orbits and ERPs. This article discusses the transition from the old to the new CODE ultra-rapid orbit and ERP products and the associated improvement in reliability and performance. All solutions used in this article were generated with the development version of the Bernese GNSS Software. The package was slightly extended to meet the needs of the new CODE ultra-rapid generation. © 2014 Springer-Verlag Berlin Heidelberg

Brodhag S.H.,Federal Office of Topography Swisstopo | Oesterling N.,Federal Office of Topography Swisstopo | Baumberger R.,Federal Office of Topography Swisstopo
Proceedings of IAMG 2015 - 17th Annual Conference of the International Association for Mathematical Geosciences | Year: 2015

To fulfil its legal obligation the Swiss Geological Survey worked out a data management strategy to solve all challenges related to data exchange, storage and supply. Basis for this strategy are several common data models covering geological data of various dimensions (from 0D to 4D) developed together with experts of the public, private and academic sector to increase acceptance of the models.

Caer T.,Cergy-Pontoise University | Maillot B.,Cergy-Pontoise University | Souloumiac P.,Cergy-Pontoise University | Leturmy P.,Cergy-Pontoise University | And 2 more authors.
Journal of Structural Geology | Year: 2015

Close to north-west front of the Jura thrust belt in Switzerland, the Mont Terri anticline is located at a disruption of the Muschelkalk decollement, due to a former normal fault. Numerous geological data are available thanks to a motorway tunnel cross-cutting the fold and an underground laboratory. Original field data, two geological maps, a borehole, and a highway tunnel constrain the inner structure. The anticline is characterized by an overturned frontal limb, a steep back limb, and a ramp cross-cutting older normal faults. Three geological cross-sections and three 2D kinematic models are proposed as various combinations of fault-bend folding, fault-propagation folding and detachment folding. The main motivation of this study is to illustrate how geometrical constructions can be constrained by the kinematic approach of limit analysis, which determines the optimal deformation, including faults, that verifies mechanical equilibrium and the Coulomb criterion. Matching some of the important kinematic steps assumed in each three interpretations to the optimal deformation leads us to define the compatible ranges of values of the frictional parameters. These ranges allow us to assess the likeliness of the important kinematic steps of each kinematic model. The present analysis provides a quantitative link between the assumed evolution of the internal structure, and the concomitant evolutions of the topography and of the frictional parameters. © 2015 Elsevier Ltd.

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