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Buechi M.W.,University of Bern | Frank S.M.,Dr. von Moos AG | Graf H.R.,Dr. von Moos AG | Menzies J.,Brock University | Anselmetti F.S.,University of Bern
Sedimentology | Year: 2017

The sedimentary infills of subglacially eroded bedrock troughs in the Alps are underexplored archives for the timing, extent and character of Pleistocene glaciations but may contain excellent records of the Quaternary landscape evolution over several glacial-interglacial cycles. The onset of sedimentation in these bedrock troughs is often reflected by diamicts and gravels directly overlying bedrock in the deepest basin segments. Subglacial or proglacial depositional environments have been proposed for these coarse-grained basal units but their characteristics and origin remain controversial. This article presents results from drill cores that recovered a coarsegrained basal unit in a major buried bedrock-trough system in the Lower Glatt Valley, northern Switzerland. The excellent core recovery allowed a detailed study combining macroscopic, microscopic and geochemical methods and gives unprecedented insights into the transition from erosion to deposition in overdeepened bedrock troughs. These results show that the basal infill comprises diamicts, interpreted as subglacial tills, separated by thin sorted interbeds, originating from subglacial cavity deposition. The stacking of these units is interpreted to represent repeated switching between a coupled and decoupled ice-bed-interface indicating an ever-transforming mosaic of subglacial bed conditions. Decoupling in response to high basal water pressures is probably promoted by the confined subglacial hydraulic conditions resulting from the bedrock acting as aquitards, the narrow reverse sloping outlet and a large catchment area. While stratigraphic and lithological evidence suggests that erosion and the onset of basal sedimentation occurred during the same glaciation, different scenarios for the relative timing of infilling in relation to formation and glaciation of the bedrock trough are discussed. Overlying deltaic and glaciolacustrine sediments suggest deposition during subsequent deglaciation of the bedrock trough. The basal sediment characteristics are in agreement with previous reports in hydrogeological and seismic exploration and suggest the occurrence of similar basal successions in other subglacially overdeepened basins in the Alps and elsewhere. © 2016 The Authors.


Letsch D.,Dr. von Moos AG
Bulletin fuer Angewandte Geologie | Year: 2012

The present article gives an overview of a Quaternary gravel body in the upper part of the Küsnachter Tobel (Küsnacht ZH]. This body fills a preexisting fluvial valley that runs slightly displaced to the recent Küsnachter Tobel. Based on sedimentological and stable isotope geochemical investigations and data from numerous unpublished drillings an attempt is undertaken to genetically interpret the gravel body. To this end it is divided into four lithofacies types. A possible genetic model into which one can place these four lithofacies types is a lake damned up by the Linth-Walensee glacier into which the latter shed glacial debris flows. Temporarily the lake fell dry as indicated by subaerial debris flow deposits. Furthermore turbidite and glacier-milk deposits deserve attention. The latter is also partly responsible for the very thorough cementation of parts of the gravel. As far as can be judged from existing data the age of the gravel body is older than the maximum of the last glaciation.


Loew S.,ETH Zurich | Lutzenkirchen V.,Dr. von Moos AG | Hansmann J.,ETH Zurich | Ryf A.,AlpTransit Gotthard AG | Guntli P.,Sieber CassinaHandke AG
International Journal of Rock Mechanics and Mining Sciences | Year: 2015

The Gotthard Base Tunnel (GBT) is a 57. km long and up to 2500 m deep railway tunnel constructed between 2000 and 2011 in the Central Alps of Switzerland. As drainage of fractured rocks by deep tunnels accompanied by significant decrease in groundwater pressure causes large-scale deformations even in hard crystalline rocks, a comprehensive surface deformation and tunnel inflow monitoring system has been established and operated for more than ten years. This paper presents the results from this monitoring system and explains the observed hydro-mechanically coupled and transient rock mass behavior based on detailed assessments of geological, geomechanical and hydrogeological conditions and conceptual continuum models. The collected data show that significant tunnel-drainage induced surface deformations also develop in rock masses with moderate hydraulic conductivity (2E-9 m/s) and small cumulative tunnel inflows (a few liters per second per kilometer). In this case deformations are caused by pore pressure reductions and rock mass deformations around the draining tunnel at depth, and not by groundwater table elevation changes. The pattern of surface settlements observed along the tunnel axis is very irregular (up to 11. cm in 2013) and strongly influenced by hectometer scale hydro-mechanical heterogeneities of steeply dipping geological units striking at large angle to the tunnel axes. At the depth of the studied tunnel section (1500-2500 m) about 50% of the surface settlements can be recorded. The surface settlements are connected to horizontal displacements and strains directed towards the tunnel axes or advancing tunnel face. The resulting horizontal displacement at the Nalps dam has reached about 65 mm in 2013. Compressive strains in the order of 20-50 microstrain are typically observed within a corridor of about 1 to 1.5 km width. Outside the reversal point of the settlement trough, extensile strains of similar magnitude develop. © 2015 Elsevier Ltd.


Lowick S.E.,University of Bern | Buechi M.W.,University of Bern | Gaar D.,University of Bern | Graf H.R.,Dr. von Moos AG | Preusser F.,Albert Ludwigs University of Freiburg
Boreas | Year: 2015

Optically stimulated luminescence (OSL) dating was applied to proglacial deposits from the Klettgau Valley in northern Switzerland, which is understood to record several phases of glaciation prior to the Last Interglacial. The aim was to provide an independent chronology for the different sedimentary units to understand better the complex depositional history of the region. This time range requires care when assessing the reliability of the luminescence protocols applied. Equivalent doses for fine- and coarse-grain quartz remained below 300 Gy, while dose response curves for both fractions continued to display growth above 500 Gy. Dose recovery tests confirmed the ability of the single aliquot regenerative (SAR) protocol to recover laboratory doses of a similar size to burial doses, and isothermal decay measurements confirmed the stability of the quartz signal. Having passed rigorous testing criteria, quartz OSL ages of up to ∼200ka were considered reliable but significantly underestimated expected ages and prompt a reconsideration of earlier interpretations of the stratigraphy for this site. Rather than representing three separate glaciations, quartz luminescence ages instead suggest that these deposits record up to four independent ice advances during Marine Isotope Stage 6. For both single grain and single aliquot feldspar dating, it was not possible to separate the conflicting influences of anomalous fading and partial bleaching. However, uncorrected feldspar central age model ages were found to be in reasonable agreement with quartz age estimates, and suggest that feldspar ages may still offer useful additional information in this region. © 2015 Collegium Boreas.


Castel J.-C.,Museum dhistoire naturelle de Geneva | Oppliger J.,Museum dhistoire naturelle de Geneva | Oppliger J.,University of Geneva | Luret M.,University of Geneva | And 4 more authors.
Quaternaire, Supplement | Year: 2011

The Geissbachhöhle is a small cave located at an altitude of 1260m-asl in the Glarus Canton (Switzerland), 800 m above the Linth valley. The cave, which is not easily accessible, was surveyed in 2005 and 2006 revealing it to be an important site for cave bears. Damage caused to the cave before its closure in 2007 prompted us to make a new survey in 2009, which considerably increased our knowledge of the cave contents. The MNI increased from 23 to 49; in many places the paleontological deposits are over 50 cm deep, and a gallery that had been thought to be empty was found to contain numerous remains hidden beneath a layer of rocks. A complete female cave bear skeleton lying in a natural posture was the source of osteometric informations. A straight scrape on the spinous process of one of the lumbar vertebrae looks rather like a cut made by a hunting weapon. A one-month-old cub found between her front legs gives a point of reference for the juveniles of this taxon. In addition to these findings, we present the first elements of a population analysis (gender ratio, age classes, etc). Several 14C dates allow us to place the Ursus spelaeus occupation of the cave between 40,000 and 50,000 BP. The material also included remains of Ursus arctos dating from the first half of the Holocene, and Capra ibex (dating in progress).


John M.,John Tunnel Consult ZTG | Matousek F.,Dr. von Moos AG | Dallapiazza W.,ILF Beratende Ingenieure AG
Geomechanik und Tunnelbau | Year: 2016

For deep tunnels with restricted possibilities for site investigation, deviations from the forecast are usually to be expected. Deviations of geological and hydrogeological conditions have different effects on tunnelling. At the Gotthard Base Tunnel it was found that some areas considered as critical actually behaved most favourably, whereas other areas, such as fault zones and zones of high rock pressure, deviated unfavourably from the forecast with considerable effects on costs and the time schedule. Unfavourable deviations could not be compensated by favourable areas. It should be also noted that these deviations had not been included in risk analyses, because they were unknown, however the original cost prognosis of 1999 provided sufficient financial reserves. These deviations were mastered by intensive probing ahead of excavation and adaptation of design, construction programme and additional measures defined during construction. On the basis of the comparison of forecast and actual conditions, the positive and negative effects of the conditions encountered on tunnelling are described. Bei einem tiefliegenden Tunnel mit beschränkten Möglichkeiten der Erkundung treten bei der Ausführung naturgemäß Abweichungen von der Prognose auf. Diese haben ihre Ursachen in den geologischen und hydrogeologischen Verhältnissen, die sich unterschiedlich auf den Vortrieb auswirken. Beim Gotthard-Basistunnel hat sich gezeigt, dass sich in einzelnen als kritisch eingestuften Bereichen das Gebirge günstiger verhalten hat als prognostiziert. Von der Prognose abweichende ungünstigere Bereiche, insbesondere Störzonen und druckhaftes Gebirge, hatten erhebliche Auswirkungen auf Kosten und Termine, die durch die günstigeren Bereiche nicht aufgewogen werden konnten. Diese Abweichungen waren in den Risikoanalysen nicht enthalten, da diese nicht bekannt waren. Allerdings waren in der ursprünglichen Kostenprognose von 1999 entsprechende finanzielle Reserven vorgesehen. Die geänderten Verhältnisse wurden mit einer intensiven Vorauserkundung erfasst; mit einer Anpassung der Planung, des Bauablaufs und dem Einsatz zusätzlicher Maßnahmen wurde ihnen Rechnung getragen und damit konnten diese zielführend bewältigt werden. Auf Basis einer Gegenüberstellung von Prognose und Befund wird aus Sicht des SIOP-Teams auf die positiven und negativen Auswirkungen der angetroffenen Verhältnisse auf den Vortrieb eingegangen. © 2016 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin


Grieder L.,Pöyry | Mehnert F.,FEDRO | Jorin U.,Dr. Von Moos AG
Underground - The Way to the Future: Proceedings of the World Tunnel Congress, WTC 2013 | Year: 2013

The Milchbuck tunnel in the City of Zurich provides one of the most important road accesses to the City Center. The single tube, 1.9 km long two-way road tunnel has been in operation since 1985. A new safety gallery is being constructed parallel to the tunnel to satisfy the increased safety requirements. It connects to five existing, blind transverse galleries. The safety gallery is designed for pedestrian use only. The tunnel drive is divided into an almost 1,000 m long rock section in the northern part and a 340 m long soil section in the southern part. From the northern portal the solid rock section starts under 10 m of overlying ground. The excavation is being carried out with a gripper TBM with a diameter of 4.15 m. The 340 m long section in the soil is being constructed starting from the southern portal where there is overlying ground of 5m at the beginning reaching up to 30 m further on. This part of the gallery is being executed by mechanical excavation equipment. The tunnel support is made by a pipe umbrella combined with lattice girders and fibre-shotcrete. Strict requirements regarding settlement of buildings and infrastructure had to be fulfilled. By the end of 2012, 100 % of the tunnel will have been excavated. The limited available space for site installations and the permanent use of the road tunnel presented challenges for the contractor's logistics and the safety precautions for the vehicle traffic. The completion of the tunnel construction is planned for 2013. © 2013 Taylor & Francis Group.


Graf H.R.,Dr. von Moos AG | Burkhalter R.,Bundesamt fur Landestopografie swisstopo
Swiss Journal of Geosciences | Year: 2016

A. Penck’s and E. Brückner’s “classical” subdivision of Quaternary deposits, developed in the Alpine foreland of southern Germany, was used for a long time as a basis for the classification of Quaternary deposits on Swiss geological maps. Due to fundamental differences between southern Germany and northern Switzerland regarding the morphogenetic control of the drainage system—especially regarding the morphostratigraphic position of various lithostratigraphic units—this subdivision should no longer be applied in Switzerland. With this in view, a new concept for a stratigraphic classification and nomenclature is presented here. It is based on the national guidelines for stratigraphic nomenclature compiled by the Swiss Committee on Stratigraphy SCS. In addition, a corresponding system for map legends is proposed. This concept has already been applied in a number of sheets of the Geological Atlas of Switzerland 1:25,000 and will be implemented in future maps. © 2016 Swiss Geological Society


Tunneling in urban regions in the Swiss midlands with thick quarternary unconsolidated rocks makes high demands on geological and hydrogeolocial investigations. Geotechnical and hydrological properties of geological formations are often altered by former man-made constructions (buildings and their basement, existing tunnels, underground lifelines and so on), which requires especially precise definitions of the spatial distribution of the even naturally complex geological bodies. Interactions between existing buildings, geological and groundwater conditions and the underground works planned have therefore to be seen as a whole. This requires also a good understanding of technical possibilties and risks by the geologist in charge. We wish to emphasize that the engineering geologist should be involved in all stages of the project development to achieve an optimized tunnel construction (costs, risk, time). Two examples of complex tunneling in Schaffhausen (suburban national highway N4) and Zurich (new national railway line below the main city, under construction), which were accompanied by the author, shall illustrate these special conditions.

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