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Leichtbeton-Bemessungstabellen zum Eurocode 6 Beton- und Stahlbetonbau 4/2016 232 Aktuell

Kurzfassung

Keine Kurzfassung verfügbar.

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Elsmeier, Kerstin; Hümme, Julian; Oneschkow, Nadja; Lohaus, Ludger Prüftechnische Einflüsse auf das Ermüdungsverhalten hochfester feinkörniger Vergussbetone Beton- und Stahlbetonbau 4/2016 233-240 Fachthemen

Kurzfassung

Hochfeste Vergussbetone finden häufig Einsatz im Bereich der Windenergieindustrie, wo sie hochzyklischen Beanspruchungen ausgesetzt sind. Bislang sind zum Ermüdungsverhalten solcher Betone jedoch vergleichsweise wenige Untersuchungsergebnisse vorhanden. Daher existieren bei der Beurteilung des Ermüdungsverhaltens hochfester Vergussbetone noch erhebliche Unsicherheiten. Am Institut für Baustoffe der Leibniz Universität Hannover konnte in ersten Untersuchungen ein abweichendes Ermüdungsverhalten von hochfesten Vergussbetonen gegenüber hochfesten Normalbetonen festgestellt werden. Die Ergebnisse der Untersuchungen deuten darauf hin, dass die auftretenden Unterschiede verschiedenen prüftechnischen Störeinflüssen geschuldet sind, die bei hochfesten Vergussbetonen einen stärkeren Einfluss auf das Ermüdungsverhalten ausüben als bei Normalbetonen. Die prüftechnischen Störeinflüsse werden insbesondere durch die Prüffrequenz hervorgerufen. Mit der Prüffrequenz einhergehend wirkt sich auch die Probekörpererwärmung infolge der zyklischen Beanspruchung auf die Ergebnisse der Ermüdungsversuche aus. In diesem Beitrag werden die Untersuchungsergebnisse hinsichtlich des Ermüdungsverhaltens hochfester Vergussbetone vorgestellt und prüftechnische Einflüsse und deren Auswirkungen auf das Ermüdungsverhalten aufgezeigt.

Technical testing influences on the fatigue behaviour of high-strength grouting mortar
High-strength grouting concretes are commonly used in the wind energy industry, where they are exposed to high cyclic stresses. However, so far, concerning the fatigue behaviour of these concretes is hardly any research available. Therefore, there are still considerable uncertainties regarding the fatigue behaviour of high-strength grouting concretes. At the Institute of Building Materials Science, Leibniz Universität Hannover, deviating fatigue behaviour of high-strength grouting concretes compared to a common high-strength concrete could be determined in first investigations. The results of the investigations indicate that the differences in the fatigue behaviour are occurring due to various technical test influences, which exercise a stronger influence on the fatigue behaviour for high-strength grouting concrete than common concrete. In particular, the testing frequency has a strong influence on the results of the fatigue investigations. Along with the testing frequency, the specimen heating due to the cyclic loading influences the results of the fatigue investigations. In this paper first results of the investigations concerning the fatigue behaviour of high-strength grouting mortar and technical testing influences and their impact on the fatigue behaviour are presented.

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Welsch, Torsten; Reißen, Karin; Schnellenbach-Held, Martina; Hegger, Josef; von Weschpfennig, Dieter; Haardt, Peter Praxiserfahrungen zum Verstärken von Betonbrücken Beton- und Stahlbetonbau 4/2016 241-252 Berichte

Kurzfassung

Steigende Beanspruchungen insbesondere durch Schwerlastverkehr und altersbedingte Tragfähigkeitsdefizite älterer Brückenbauwerke führen dazu, dass zahlreiche Betonbrücken instand gesetzt oder verstärkt werden müssen. Um einen Beitrag zur konstruktiv und wirtschaftlich erfolgreichen Durchführung zukünftiger Verstärkungsmaßnahmen zu leisten, wurde im Auftrag der Bundesanstalt für Straßenwesen (BASt) eine Erfahrungssammlung zu “Verstärkungen älterer Beton- und Spannbetonbrücken” erstellt [1]. In der Dokumentation wird ein Überblick über den Stand der Technik der im Massivbrückenbau eingesetzten Verstärkungstechniken gegeben, und insgesamt 76 durchgeführte Verstärkungsmaßnahmen werden ausgewertet. Repräsentative Verstärkungsmaßnahmen werden in anonymisierter Form detailliert vorgestellt. Der vorliegende Bericht gibt einen Überblick über die in Kürze erscheinende Erfahrungssammlung [1], wobei die wesentlichen Erfahrungen der ausgewerteten Anwendungsfälle vorgestellt werden.

Experiences on the Strengthening of Concrete Bridges
Increasing loads, in particular by heavy-duty traffic, and age-related load-bearing deficits of older bridges result in the need of repairing and strengthening numerous concrete bridges. In order to contribute to a successful realization of future strengthening measures, a collection of experiences focusing on economical and constructive perspectives was provided on behalf of the German Federal Highway Research Institute (BASt). In this documentation [1], an overview is given on the state of the art of strengthening technologies for reinforced and prestressed concrete bridges, and the experiences of 76 strengthening measures are summarized. Representative strengthening measures are presented in anonymized form. This report describes the new documentation [1], and essential experiences of the evaluated cases of application are introduced.

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Bau des Wasserkraftwerks Lauca am Kwanza in Angola Beton- und Stahlbetonbau 4/2016 252 Aktuell

Kurzfassung

Keine Kurzfassung verfügbar.

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Beton- und Stahlbetonbau aktuell 4/2016 Beton- und Stahlbetonbau 4/2016 253-259 Beton- und Stahlbetonbau aktuell

Kurzfassung


Persönliches:
Verdienstorden der Bundesrepublik Deutschland an Prof. W. KRÄTZIG verliehen

Nachrichten: Teilnehmerrekord bei den 60. BetonTagen / solidian gewinnt “Innovationspreis der Zuliefererindustrie Betonbauteile” / Planerkonjunktur bleibt ungetrübt / Verleihung Schöck Bau-Innovationspreis / Kochertalbrücke und Donausteg Deggendorf gewinnen Deutschen Brückenbaupreis 2016

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Zuschrift zu: Schubverhalten von Biegebauteilen ohne Querkraftbewehrung Beton- und Stahlbetonbau 4/2016 259-263 Zuschrift

Kurzfassung

Zuschrift von RICHARD ROJEK, Friedberg, zu: TUE, N. V.; THEILER W.; TUNG, N. D.: Schubverhalten von Biegebauteilen ohne Querkraftbewehrung. Beton- und Stahlbetonbau 109 (2014), Heft 10, S. 666-677
Erwiderung der Autoren

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Kongresse - Symposien - Seminare - Messen Beton- und Stahlbetonbau 4/2016 264-265 Veranstaltungskalender

Kurzfassung

Keine Kurzfassung verfügbar.

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Content: Geomechanics and Tunnelling 4/2016 Geomechanics and Tunnelling 4/2016 289 Content

Kurzfassung

Keine Kurzfassung verfügbar.

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Ayaydin, N. Tunnelling in Turkey Geomechanics and Tunnelling 4/2016 290-291 Editorials

Kurzfassung

Keine Kurzfassung verfügbar.

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News: Geomechanics and Tunnelling 4/2016 Geomechanics and Tunnelling 4/2016 292-299 News

Kurzfassung

• Implenia to extend Metro Line 11 for the Grand Paris Express project / Implenia verlängert U-Bahn-Linie 11 für das Projekt Grand Paris Express
• Tunnelling machine for the Eppenberg Tunnel accepted / Vortriebsmaschine für den Tunnel Eppenberg abgenommen
• Ground breaking for the Brenner contract Eisack / Spatenstich für das Brenner-Baulos Eisack
• Züblin wins award worth 400 million in Chile / Züblin erhält in Chile Auftrag in Höhe von 400 Millionen
• Planning decision for the first section at Stuttgart Airport / Planfeststellungsbeschluss für ersten Abschnitt am Stuttgarter Flughafen
• Successful tunnel breakthrough at Obervermuntwerk II / Erfolgreicher Stollendurchschlag beim Obervermuntwerk II
• Femern A/S signs main contracts with a value of EUR 4 billion / Femern A/S unterzeichnet Hauptbauverträge im Wert von 4 Mrd. Euro
• Robbins and NHI agree to a three-phase merger plan / Robbins und NHI vereinbaren Dreistufenplan zur Fusion
• Terratec supllies TBMs for Turkey, Thailand and India
• Call for papers - Themes for the next issues of Geomechanics and Tunnelling / Themen für die nächsten Ausgaben der “Geomechanics and Tunnelling”

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Arioglu, Basar; Gokce, Hasan Burak; Malcioglu, Fatma Sevil; Arioglu, Ergin TBM Tunnel under the Bosphorus for the Istanbul Strait Road Crossing Project Geomechanics and Tunnelling 4/2016 303-309 Topics

Kurzfassung

The population increase in Istanbul is also reflected in car ownership, which brings an extensive traffic load to the city, especially to the two bridges over the Bosphorus. After feasibility studies, a double deck, 3.4 km subsea tunnel with a 13.7 m diameter at a maximum depth of 106 m below sea level and a capacity of 100,000 cars/day was initiated as a solution for the city. The tunnel, excavated by a custom-made mixshield slurry TBM, passes through very complex geological structures including the Trakya formation, transition zones and marine sediments in a highly seismic area.

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Gokce, Hasan Burak; Demir, Korhan; Bakir, Ayd?n; Aribilginc, Tamer; Arioglu, Ergin Asia Transition Box and Conventionally Excavated Twin Tunnels for the Istanbul Strait Road Crossing Project Geomechanics and Tunnelling 4/2016 310-316 Topics

Kurzfassung

The 14.6 km long Istanbul Strait Road Crossing Project is a safe, quick and environmentally responsible alternative road link between Asia and Europe, as such it is being constructed under a Build-Operate-Transfer contract by a public-private partnership. The investor/contractor has committed to build the Project in 55 months and to operate the facility for a concession period of approximately 25 years. This article examines the project's two critical structures located in the Asian side of Istanbul, considering site investigation, construction and monitoring. The first structure is a cut and cover construction next to the Bosphorus, called the Asia Transition Box (ATB), which enabled the launching of the TBM and conventional tunnels. The second is the conventionally excavated twin tunnels (CETT), which pass under a highly urbanized part of Istanbul and provide the transition from the highway into the tunnel under the Bosphorus.

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Özcan, Bar?s; Duman, Emre; Türkoglu, Aykut; Kayal?, Sanem; Saenz, Ignacio Design and construction of the mined K?s?kl? Station on the Üsküdar-Çekmeköy Metro Line Project Geomechanics and Tunnelling 4/2016 317-325 Topics

Kurzfassung

The Üsküdar-Çekmeköy Metro Line (UCM), which is located on the Asian side of Istanbul, is an 18 km underground metro line with 27 km of TBM tunnel, 13 km of NATM tunnel and 16 stations. Apart from being a completely tunnelled station, it has several other features. It is the deepest station in this metro line with the platform depth 45 m below surface level. The station is being built in a complex geology that contains several passive fault zones. The ticket hall and technical rooms are also located in an NATM tunnel with an excavated width of 20 m. Most of the passenger circulation is planned to be carried out by elevators.
The station has been designed with two levels of NATM tunnels with four main elliptical shafts. The geology varies from very strong quartz arenite with a compressive strength of 77 MPa to highly weathered fault zones containing andesite. The complex geometry and geology of the station dictated utmost care for excavation and final lining design of the NATM sections in order to provide stability during excavation and sufficient structural capacity in case of a seismic event.

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Tokgöz, Nuray An assessment method for fine-grained sedimentary materials excavated by EPB TBM Geomechanics and Tunnelling 4/2016 326-337 Topics

Kurzfassung

The aims of this study are to find a solution for the problems (lumping, adhesion, and clogging) encountered with fine-grained sedimentary materials, minimize the time and cost of excavation, and decrease the potential environmental effects due to soil conditioning chemicals used in the process of excavating a waste water tunnel. Therefore, this study will contribute important technical knowledge regarding design and implementation of excavation with TBM to the mining and construction industries as well as for optimization in mechanical engineering.
In this research, real-time machine operational parameters recorded by EPB TBM and actual geotechnical parameters in an Istanbul-Büyükcekmece Wastewater Tunnel at seven selected tunnel sections were used as input data for the back analysis and assessment method. The method covers excavated materials with: (1) water and (2) soil conditioning chemicals. The influence of water and soil-conditioning chemicals of different proportions on torque, thrust, advance rate of the TBM, and plasticity and consistency indices of the material were investigated. Finally, integrated data were evaluated by multiple linear regression models.

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Kohlböck, Bernhard; Koc, Onur; Ayten, Türkay Istanbul Strait Road Tube Crossing: Design of NATM Tunnels and Asian Transition Box Excavation Geomechanics and Tunnelling 4/2016 338-344 Topics

Kurzfassung

Istanbul is among the fastest growing megacities in the world and the only one located on two continents, divided by the Bosphorus strait. The geographic situation together with the enormous growth of population impose great challenges, especially considering urban and infrastructure development. The Bosphorus Strait Road tunnel, also called Eurasia Tunnel, is the first road tunnel connecting the European and the Asian side of the city with the aim of alleviating Istanbul's traffic pressure and reducing the travel time between Kazlıçeme and Göztepe from 100 to 15 minutes. This article focuses on the design of the twin tunnels and the transition box from NATM to TBM on the Asian side.

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Shalabi, Faisal I.; Cording, Edward J.; Paul, Stanley L. Sealant behavior of gasketed segmental tunnel lining - Conceptual model Geomechanics and Tunnelling 4/2016 345-355 Topics

Kurzfassung

Gasket sealant behavior along joints of concrete tunnel lining depends on gasket-gasket and gasket-groove contact loads, bonding between gasket and groove, and gasket lateral extrusion. As the gaskets are made of polymers, gasket contact loads are expected to drop with time due to relaxation. Reduction in the contact load with time is expected to affect the gasket sealant capacity. Gasket-gasket contact loads depend on many factors such as: stiffness of the gasket material, gasket shape and volume, groove size and configuration, gasket base configuration, and the amount of gasket compression. In this work, the mechanical and sealant behavior of gaskets in grooves were investigated. Two types of gaskets were considered: open base gasket for low design water pressure (less than 600 kPa), and closed base gasket for high water pressure (up to 4###, 000 kPa). The work focused on gasket-in-groove load deformation behavior and gasket sealant potential including the effect of gasket contact loads, relaxation, extrusion, and the change in joint gap during water pressurization. The effect of gasket base conditions (fingers base vs. closed base) on the gasket sealant behavior was also considered in this work. A conceptual model was developed that explains the leakage of the gasket as water pressure is applied.

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Paternesi, Alessandra; Schweiger, Helmut F.; Schubert, Peter Verification of a rheological constitutive model for shotcrete through back-analysis Geomechanics and Tunnelling 4/2016 356-361 Topics

Kurzfassung

Tunnel excavation represents a particularly challenging problem from the design point of view, mainly due to the uncertainties characterising the soil or rock mass behaviour and to the difficulties in the prediction of the stress state on the structural supports. This explains why tunnel designers mostly rely on observational data, adapting excavation sequences and support measures during the construction phase (at least in the case of traditionally excavated tunnels), especially for deep tunnels, where the geological and geotechnical uncertainties can be significant. However, the observational method requires a reliable monitoring system as well as considerable work to interpret and back-analyse data measured during construction. On the other hand, this interpretation and back-analysis represent an important step in gaining better understanding of the system response and allowing improvement of the design, thus avoiding excessively conservative and uneconomical solutions. In this paper, a back-analysis of stress and displacement measurements is presented for a NATM tunnel excavation in rock, carried out using a rheological model for shotcrete. It is shown, consistently with the previous literature on the topic, that the use of an advanced model improves the prediction of tunnel behaviour compared to the common practice of using quasi-elastic E-moduli.

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Diary of Events: Geomechanics and Tunnelling 4/2016 Geomechanics and Tunnelling 4/2016 362 Diary of Events

Kurzfassung

Keine Kurzfassung verfügbar.

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Inhalt: Geotechnik 4/2016 geotechnik 4/2016 Inhalt

Kurzfassung

Keine Kurzfassung verfügbar.

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Balthaus, Hansgeorg Vergabeverfahren mal anders - oder "Novel Bidding" geotechnik 4/2016 223 Editorials

Kurzfassung

Keine Kurzfassung verfügbar.

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Sondermann, Wolfgang Was macht einen guten Ingenieur aus? geotechnik 4/2016 224 Vom Vorsitzenden

Kurzfassung

Keine Kurzfassung verfügbar.

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Köditz, Jens; Wudtke, Robert-Balthasar; Witt, Karl Josef Gegenüberstellung direkter und indirekter Versuchsmethoden zur Bestimmung der Zugfestigkeit bindiger Böden geotechnik 4/2016 225-234 Fachthemen

Kurzfassung

Bei allen Arten der Rissinitiation in bindigen Böden ist deren Zugfestigkeit die wesentliche Kenngröße des Materialwiderstands. Direkte und indirekte Methoden zur experimentellen Ermittlung der Zugfestigkeit wurden an unterschiedlich bindigen Böden vergleichend bei verschiedenen Proctor-Verdichtungsgraden und Wassergehalten an gesättigten und ungesättigten Proben durchgeführt. Anhand der Versuchsergebnisse werden Aussagen zu Präzision, Zuverlässigkeit und Qualität der Versuchsmethoden abgeleitet, welche Entscheidungsgrundlagen zur Festlegung der für eine spezielle Fragestellung angemessenen Versuchsmethode sind.

Comparison of direct and indirect test methods for determining the tensile strength of cohesive soils.
Related to the initiation of cracks in cohesive soils, the tensile strength is the most important parameter concerning resistance. Direct and indirect methods for the experimental determination of the tensile strength of different cohesive soils were comparatively investigated and evaluated. The experiments were carried out on saturated and unsaturated specimen at various degrees of compaction and water content. Based on the results, the different experimental approaches are compared in respect to precision and reproducibility. This comparison and evaluation might be a basis to find the appropriate test method for a specific impact.

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Lempp, Christof; Menezes, Flora; Sachwitz, Simon Tonstein als Wirtsgestein: Ein geomechanischer Beitrag über Opalinuston geotechnik 4/2016 235-251 Fachthemen

Kurzfassung

Der Opalinuston ist ein prominenter Vertreter der organikhaltigen Tonsteine oder Schiefertone, die in der Schichtenfolge aus Trias und Jura regional ein mehrere Zehnermeter mächtiges, relativ homogenes Schichtpaket bildet. In Abhängigkeit vom Verfestigungsgrad der Pelitgesteine variieren die geomechanischen Parameter Scherfestigkeit, Zugfestigkeit und Durchlässigkeit, die bei einer zu diskutierenden Nutzung als Wirtsgestein für die Lagerung radioaktiver Abfälle auch bautechnische Bedeutung erlangen. Ein Tunnelvortrieb im Opalinuston bot die eher seltene Gelegenheit, Proben aus unverwittert frischen Schiefertonen in größerem Umfang als bei üblichen Bohrungen zu gewinnen. Es werden geomechanische Laborversuche, insbesondere mehrstufige, triaxiale Kompressionsversuche und Hydraulic-Fracturing-Versuche an definiert räumlich eingespannten Quaderproben ausgewertet, um Scherfestigkeit, hydraulische Zugfestigkeit sowie Durchlässigkeits- bzw. Abdichtungseigenschaften des Opalinustons zu charakterisieren. Einführend wird in diesem Kontext die Bedeutung des Sättigungszustands und dessen Veränderlichkeit diskutiert. Die ermittelten geomechanischen Parameter werden verglichen mit vormals höher und mit ähnlich beanspruchten, äußerlich gleich erscheinenden Pelitgesteinen aus Japan und aus der Schweiz.

Clay shale as host rock:
a geomechanical contribution about Opalinus clay. The Opalinuston is a prominent rock representing the type of organic clay shales or clay stones within the sequence of Triassic and Jurassic marine sediments in Southern Germany. The rock forms a homogenous unit some ten meters thick. The degree of consolidation of this type of pelitic rock depends mainly on the former load conditions, but is also dependent on the long-term weathering and even on the present exposition. The geomechanical parameters such as shear strength, tensional strength and permeability vary with the state of consolidation and become important when the use is discussed of such rocks for radioactive waste disposal.
A tunneling project at the northern escarpment of the Swabian Alb (Southwest Germany) within the Opalinus clay offered the rare opportunity to obtain fresh unweathered rock samples in greater amounts compared to fresh drilling cores from which geomechanical investigations are usually undertaken. Consequently, the results of geomechanical laboratory testings are presented in order to compare here the results of multistep triaxial compression tests, of hydraulic fracturing laboratory tests and of some other tests for rock characterization with the corresponding results of Opalinus clay sites in Switzerland that were investigated by the Swiss Nagra Company for host rock characterization.
After a discussion of the relevant state of fresh Opalinus clay, especially of suction pressure conditions and saturation state, the results of triaxial shear tests are presented. Increasing shear deformation at increasing pressure and unchanged water saturation do not result in a significant strength reduction of the Opalinus clay. The rock shows increasing cohesion and stiffness, if multiple loading has repeatedly reached the failure point. Thus there is no increased permeability with continued shearing. Only at the beginning of the shearing process is a temporarily increased permeability to be expected due to dilatation processes. An increased permeability, however, is generated by hydraulically injected water when fracturing may occur. Such fracturing depends on the injection rate: Low injection rates lead to local structural disintegration, higher injection rates result in single crack propagation as is known from hydraulic fracturing tests. Such hydraulically formed fractures later tend to close with an increase of surrounding stress. This closure increase is comparable to a healing process because new hydraulic fractures can be generated consequently at higher stress levels. Such laboratory test results seem to be favorable when using fresh Opalinus clay as a host rock, but they are difficult to verify at standard in-situ-conditions with weathered or partly deconsolidated rocks.
Similar organic-rich and differently overconsolidated pelitic rock types display a wide spectrum of geomechanical behaviors despite the fact that no visible or physical differences can be provided. A direct comparison of the Opalinus clay parameters from the Swabian Alb, as investigated here, and from Switzerland, as determined by the Nagra Company, show differences in the effective shear strength. Nevertheless, the scatter is much smaller than that occurring for undrained shear stress differences as a function of water content.
Consequently, for each project one must define exactly the relevant conditions within the different pelitic rocks in order to determine the useful geomechanical parameters. Additionally, it can be an advantage to use great depths because of the favorable geomechanical characteristics of Opalinus clay at high pressure. In this way some of the construction problems in Opalinus clay may be reduced if not avoided by using deep boreholes for waste deposition.

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Jung, Stefan; Vrettos, Christos Bettungsmodul für Trägerbohlwände in mitteldichtem Sand aus an einem Großversuch validierten FEM-Berechnungen geotechnik 4/2016 252-262 Fachthemen

Kurzfassung

In der Baugrubenstatik für Trägerbohlwände können die haltenden Kräfte vor dem im Baugrund einbindenden Teil des Trägers mithilfe eines Bettungsmoduls berücksichtigt werden. Ein realitätsnaher Ansatz hierfür muss in der Lage sein, die Abhängigkeit der tatsächlich mobilisierten Erdwiderstandsspannungen von den Verschiebungen und der Wandgeometrie wiederzugeben. Dies war das Ziel der hier vorgestellten Parameterstudie. Die Berechnungen wurden anhand eines 3D-Modells nach der Finiten-Elemente-Methode (FEM) unter Verwendung eines nichtlinearen, elasto-plastischen Stoffgesetzes für einen typischen mitteldichten Sand, welches anhand bodenmechanischer Laborversuche kalibriert wurde, durchgeführt. Das numerische Modell wurde an Messergebnissen eines instrumentierten Großversuchs validiert. Die maßgebenden Einflussfaktoren auf Größe und Verlauf des Bettungsmoduls wurden an repräsentativen Wandsystemen untersucht. Die Ergebnisse belegen den starken Einfluss der Verschiebung, der Tiefenlage und der Druckflächenbreite. Aus den Parameterstudien wurde ein iterativer, nichtlinearer Berechnungsansatz für den Bettungsmodul hergeleitet.

Subgrade reaction modulus for soldier pile walls in medium-dense sand from FEM calculations validated on a large-scale test.
In the structural analysis of soldier pile walls, the resisting forces in the soil in front of the embedded pile can be modelled my means of a modulus of subgrade reaction. An adequate approach to this must be able to reproduce the dependency of the actually mobilized earth resistance stresses on the displacements and on the wall geometry. This was the aim of the parametric study presented herein. The calculations were carried out using a 3D model based on the finite element method (FEM) by adopting a nonlinear, elasto-plastic constitutive law for a typical sand of medium density that has been calibrated from laboratory soil tests. The numerical model has been validated on data obtained from an instrumented large-scale field test. The factors affecting the magnitude and the distribution of the subgrade reaction modulus were investigated on representative wall systems. The results show the strong influence of the displacement, the depth coordinate, and the width of the beam. The numerical results of the parametric study were subsequently used to derive an iterative, nonlinear relationship for the horizontal subgrade reaction modulus.

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Simo, Eric Kuate; Breustedt, Michael; Müller-Hoeppe, Nina; Missal, Christian; Stahlmann, Joachim Bewertung der Barriereintegrität auf der Basis der effektiven Spannung mit dem Dilatanz- und Fluiddruckkriterium geotechnik 4/2016 263-274 Fachthemen

Kurzfassung

Die Barriereintegrität ist von zentraler Bedeutung für die Langzeitsicherheit von Endlagern für radioaktive Stoffe im Salinar. Die Integrität der Salzbarriere wird durch die Einhaltung des Dilatanz- und Fluiddruckkriteriums nachgewiesen. Während das Fluiddruckkriterium das Versagen des Gebirges aufgrund eines Lösungsdrucks beschreibt, stellt das Dilatanzkriterium das Versagen des Gebirges durch eine Scherbeanspruchung dar. Wird das Fluiddruckkriterium in den effektiven Spannungen nach Terzaghi formuliert, ist es äquivalent mit einer kleinsten effektiven Spannung von null. Da die aufnehmbare Oktaederschubspannung beim Dilatanzkriterium nach Cristescu und Hunsche von der Oktaedernormalspannung abhängig ist, wird untersucht, welchen Einfluss das Effektivspannungskonzept nach Terzaghi auf das Dilatanzkriterium hat. Am Beispiel einer generischen Abbaureihe werden die Bereiche, in denen beide Kriterien verletzt sind, für die ursprüngliche Formulierung und für die Formulierung unter Berücksichtigung der effektiven Spannungen verglichen. Die numerischen Berechnungen erfassen einen Zeitraum von 80 Jahren nach der Auffahrung bis 1.000 Jahre nach Verfüllung der Abbaue.

Evaluation of the Barrier Integrity Based on Effective Stresses Using the Dilatancy and Fluid Pressure Criterion.
For the long-term safety of repositories for radioactive waste in rock salt the integrity of the rock salt barrier is of major importance. Barrier integrity is considered to be demonstrated when the dilatancy and the fluid pressure criterion are met. While the fluid pressure criterion describes hydraulic failure due to fluid pressure the dilatancy criterion describes the failure due to shear stress. If the fluid pressure criterion is given in terms of effective stress according to Terzaghi, it is equivalent to an effective minimum stress component of zero. When using the dilatancy criterion according to Cristescu and Hunsche, the octahedral shear stress bearing capacity depends on the isotropic stress. It is investigated what happens if the concept of effective stresses according to Terzaghi is applied to the dilatancy criterion. Based on a series of generic cavities, the regions where both criteria are exceeded are compared using both the original formulation as well as the version that takes into account the concept of effective stresses. The numerical simulations comprise a time period between 80 years after cavities' excavation and 1.000 years after the cavities have been backfilled.

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