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Geotechnical Engineering (geotechnical + engineering)

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Engineering	90%

Selected Abstracts

Einbindetiefen und Schnittgrößen bei gestützten Wänden mit beliebiger Fußauflagerung

BAUTECHNIK, Issue 9 2009
Achim Hettler Univ.-Prof.
Geotechnik; Bodenmechanik; Geotechnical Engineering; Soil Mechanics Abstract Dieser Beitrag beinhaltet die Ermittlung von Schnittgrößen und Einbindetiefen bei gestützten Wänden. Zunächst wird ein Modell der Fußauflagerung vorgestellt, das sowohl eine freie Auflagerung, eine Teil einspannung als auch eine volle Einspannung umfasst. Die erforderliche Einbindetiefe lässt sich durch Ansatz von Bemessungsgrößen wesentlich einfacher berechnen als am System mit charakteristischen Größen. Bei einer teilweisen Einspannung im Boden können durch Vorgabe eines Drehwinkels im theoretischen Auflagerpunkt die charakteristischen Bodenreaktionen eindeutig festgelegt werden. Für den Fall, dass nur ständige Einwirkungen auftreten, können charakteristische Größen und Bemessungsgrößen durch einen Faktor ineinander umgerechnet werden. Eine weitere Vereinfachung ergibt sich, wenn man, den Empfehlungen des Arbeitskreises "Baugruben" folgend, die veränderlichen Einwirkungen mit einem Erhöhungsfaktor vergrößert und wie für den Lastfall mit ständigen Einwirkungen behandelt. Embedment depths and sectional forces for propped walls with different foot supports. In the following contribution the calculation of the embedment depth and the sectional forces is treated for the case of propped walls. A model for the earth support at the foot of the wall is presented including a free, a partly fixed and a fixed earth support. The determination of the embedment depth at the system with design loads is essentially easier compared to a calculation with characteristic quantities. Assuming a value for the rotation angle at the theoretical foot point of the wall permits to calculate the magnitude of the characteristic soil reactions. In the case that only permanent actions react on the wall, characteristic and design quantities are related by a simple factor. According to the recommendations of excavations a further simplification is possible, if the transient actions are increased by a factor and are treated as in the case of permanent situations. [source]

Reduktion der Frosthebungen bei der künstlichen Bodenvereisung

BAUTECHNIK, Issue 9 2009
Guoqing Zhou Prof. Dr.-Ing.
Geotechnik; Bodenmechanik; Geotechnical Engineering; Soil Mechanics Abstract Mit dem Ziel der Reduktion der Frosthebungen bei der künstlichen Bodenvereisung wurden die Einflüsse des Temperaturgradienten, der Temperaturänderung sowie der Temperaturänderungsamplitude und -periode der Vereisungstemperatur auf die Frosthebungen bei der eindimensionalen Frosteindringung in feinkörnige Böden experimentell im Labor untersucht. Bei der Frosteindringung in feinkörnige Böden ist die Frosthebung infolge der Bildung der untersten Eislinse (letzte Eislinse bei Frostung von oben nach unten) im thermodynamisch stationären Zustand maßgebend. Der Temperaturgradient beeinflusst zwar die Frosteindringtiefe, die Größe der Frosthebung dagegen nur in geringem Maße. Durch zyklische Veränderungen der Vereisungstemperatur kann das Wachstum der letzten Eislinse beschränkt und dadurch die Frosthebung vermindert werden. Die zyklische Veränderung der Vereisungstemperatur bereits vor der Bildung der letzten Eislinse führt dagegen zu einer großen Frosthebung. Zur Minimierung der Frosthebung müssen die Temperaturveränderungsamplitude und -periode während der Vereisung auf die Eislinsenbildung abgestimmt werden. Decreasing frost heaves of artificial frozen soils by intermission freezing. For decreasing the frost heaves of artificially frozen soils the influences of temperature gradient, its changes as well as the amplitude and period of changing freezing temperature on the one-dimensional frost heaves of fine-grained soils were investigated by experiments in the laboratory. During the frost penetration into the fine-grained soils the frost heaves due to the formation of the final ice lens under thermodynamic stationary condition is decisive. The gradient of temperature influences strongly the depth of frost penetration but only little the total frost heave. Cyclical changes of the freezing temperature can confine the growth of the final ice lens and thereby the frost heave decreases. However, the cyclical changes of the freezing temperature before the formation of the final ice lens can cause a heavy frost heave. For decreasing frost heaves the amplitude und period of changing the freezing temperature must be controlled properly. [source]

Untersuchungen zum vertikalen Tragverhalten von Spundwänden

BAUTECHNIK, Issue 8 2009
Jürgen Grabe Univ.-Prof.
Geotechnik; Bodenmechanik; Geotechnical Engineering; Soil Mechanics Abstract Spundwände werden im Wesentlichen auf Biegung infolge einer Belastung durch Erd- und Wasserdrücke beansprucht. Sie können aber auch zum Abtrag von Vertikallasten dienen. Das Tragverhalten von Spundwänden ist bei genauer Betrachtung äußerst komplex, da diesem eine räumlich und zeitlich gekoppelte Boden-Bauwerk-Interaktion zugrunde liegt. Für die praktische Bemessung muss das Tragverhalten daher stark idealisiert werden. Die Rechtfertigung der dafür notwendigen Modellvorstellungen sowie deren Vereinfachungen und Annnahmen sind, wie häufig in der Geotechnik, hauptsächlich durch Erfahrung begründet. Researching the vertical load bearing behaviour of sheet piles. Sheet pile walls are mainly used to carry loads caused by earth and water pressure via bending. In special cases these walls can be used to transfer vertical loads to the subsoil. The complex load bearing behaviour of sheet pile walls is caused by the sterical and temporal coupled soil structure interaction. For practical design the load bearing behaviour needs to be idealised. The apologies used to explain the model conceptions as well as their simplifications are, as usual in geotechnics, mainly motivated by operating experience. [source]

Geomechanics and Tunnelling 2/2010

GEOMECHANICS AND TUNNELLING, Issue 1 2010
Article first published online: 24 FEB 2010
Semmering and Koralm tunnels Neue Südbahn, Semmering und Koralm Tunnel F. Bauer: Investment in the Austrian rail network , overview of new and upgrading projects , Investitionen in das österreichische Schienennetz , Überblick Neu- und Ausbauvorhaben G. Gobiet and D. Haas: New Semmering Base Tunnel project , an interdisciplinary challenge , Semmering Basistunnel Neu , eine interdisziplinäre Herausforderung A. Fasching, R. Vanek, Th. Stadlmann, P. Reichl, G. Domberger, G. Forstinger and O. Wagner: New Semmering Base Tunnel , the investigation programme 2008/2009 and the knowledge gained in the areas of geology, hydrogeology and geotechnical engineering , Semmering-Basistunnel Neu , Das Erkundungsprogramm 2008/2009 und die daraus gewonnenen Erkenntnisse auf den Gebieten der Geologie, Hydrogeologie und Geotechnik J. Daller, A. Vigl and O. Wagner: New Semmering Base Tunnel , the current state of tunnel design taking the newest investigation results into account , Semmering-Basistunnel Neu , Aktueller Stand der Tunnelplanung unter Berücksichtigung der neuesten Erkundungsergebnisse R. Bopp, V. Langer, Ch. Neumann and O. Wagner: The ventilation and tunnel safety concept for the New Semmering Base Tunnel , Das Lüftungs- und Tunnelsicherheitskonzept für den Semmering-Basistunnel Neu G. Harer and J. Koinig: Current state of design, investigation and construction work at the Koralm Tunnel , Aktueller Stand der Planungs-, Erkundungs- und Ausführungsarbeiten beim Koralmtunnel P. Schubert, H. Hölzl, P. Sellner and F. Fasching: Geomechanical knowledge gained from the Paierdorf Investigation Tunnel in the section through the Lavanttal main fault zone , Geomechanischer Wissenszuwachs durch den Erkundungstunnel Paierdorf im Abschnitt der Lavanttaler Hauptstörungszone D. Handke, M. Nolden, K. Mussger and A. Steidl: Solution methods for the design and construction of contract KAT 3 , Lösungsansätze für Planung und Bauausführung des Bauloses KAT 3 M. Vill, H. Wagner, A. Schweighofer, H. Huber, W. Pichler and J. Kollegger: New development of a crack-limited invert slab , Neuentwicklung der rissebeschränkten Sohlplatte M. Stopka: Hengsberg Tunnel , the construction contract as seen by the contractor , Hengsbergtunnel , der Bauvertrag aus Sicht des Auftragnehmers T. Schachinger, H. Gaube and G. Krainer: Results from the Untersammelsdorf test field for the planning of the tunnelling work , Erkenntnisse aus dem Versuchsfeld Untersammelsdorf für die Gestaltung der Vortriebsmaßnahmen K. Chmelina and K. Rabensteiner: Improvement of the safety and profitability of tunnel drives through the use of automated measurement and alarm systems , examples in practice , Verbesserung der Sicherheit und Wirtschaftlichkeit von Tunnelvortrieben durch den Einsatz automatisierter Mess- und Alarm-systeme , Ausführungsbeispiele [source]

The Development of the Observational Method

GEOMECHANICS AND TUNNELLING, Issue 5 2008
Wulf Schubert o.Univ.-Prof.
A continuous observation during construction always has been an important element of geotechnical engineering for minimizing risks. The reasons are the uncertainties in the geological and geotechnical models, as well as the limited capability to sufficiently accurately describe the complex ground behaviour. In the early days design of geotechnical structures thus was mainly based on experience. As usual, experience was used to develop mathematical solutions to the problem. To account for the inherent scatter of parameters and uncertainties in the models, the assumptions made during design had and have to be verified or falsified during construction by observations. For safe and economical construction, the design has to be adjusted during construction to the actual conditions. The term "observational method" was first formally introduced by Peck and Terzaghi. The original ideas behind the method have not always been understood or followed. After a brief historical review of the observational method the current status of the method is critically reviewed, and further developments discussed. Die Beobachtungsmethode einst und jetzt Die Schwierigkeit, den Baugrund ausreichend zu erkunden und dessen Interaktion mit dem Bauwerk zutreffend mathematisch zu modellieren, erfordert die laufende Beobachtung während des Baus, um die Baumaßnahmen an die tatsächlichen Verhältnisse anzupassen und das Risiko vermindern zu können. Mit vermehrter Erfahrung wurden auch Analysemodelle entwickelt. Zur Berücksichtigung der unvermeidlichen Streuung der Baugrundeigenschaften und der Unsicherheiten in den Modellen wurden und werden während des Baus Beobachtungen durchgeführt. Die Bezeichnung "Beobachtungsmethode" wurde formal von Peck und Terzaghi eingeführt. Die damals formulierten Grundsätze wurden nicht immer verstanden und befolgt. Im Beitrag wird nach einem kurzen historischen Rückblick über Entstehung und Entwicklung der Methode der derzeitige Stand kritisch beleuchtet, und weitere Entwicklungen werden diskutiert. [source]

Lateral force and centroid location caused by horizontal and vertical surcharge strip loads on a cross-anisotropic backfill

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 13 2007
Cheng-Der Wang
Abstract This work presents analytical solutions for determining lateral force (force per unit length) and centroid location caused by horizontal and vertical surcharge surface loads acting on a cross-anisotropic backfill. The surcharge loading types are point load, line load, uniform strip load, upward linear-varying strip load, upward nonlinear-varying strip load, downward linear-varying strip load, and downward nonlinear-varying strip load. The planes of cross-anisotropy are assumed parallel to the backfill ground surface. The proposed solutions, derived by integrating the lateral stress solutions (Int. J. Numer. Anal. Meth. Geomech. 2005; 29:1341,1361), do not exist in literature. Clearly, the type and degree of material anisotropy, loading distance from the retaining wall, and loading types markedly impact the proposed solutions. Two examples are utilized to illustrate the type and degree of soil anisotropy, and the loading types on the lateral force and centroid location in the isotropic/cross-anisotropic backfills generated by the horizontal and vertical uniform, upward linear-varying and upward nonlinear-varying strip loads. The parametric study results demonstrate that the lateral force and centroid location accounting for soil anisotropy, loading distance from the retaining wall, dimension of the loading strip, and loading directions and types differ significantly from those estimated using existing isotropic solutions. The derived solutions can be added to other lateral pressures, such as earth pressure or water pressure, required for stability and structural analysis of a retaining wall. Additionally, they can simulate realistically actual surcharge loading problems in geotechnical engineering when backfill materials are cross-anisotropic. Copyright © 2007 John Wiley & Sons, Ltd. [source]

Visual framework for development and use of constitutive models

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS, Issue 15 2002
Youssef M. A. Hashash
Abstract Advanced constitutive relations are used in geotechnical engineering to capture measured soil and rock behaviour in the laboratory, and in numerical models to represent the material response. These constitutive relations have traditionally been difficult to use, understand, and develop except by a limited number of specialists. This paper describes a framework for transforming the representation of constitutive relations, as well as stress and strain quantities from a series of mathematical equations and matrix quantities to multidimensional geometric/visual objects in a dynamic interactive colour-rich display environment. The paper proposes a shift in current approaches to the development of constitutive equations and their use in numerical simulations by taking advantage of rapid advancements in information technology and computer graphics. A novel interactive visualization development and learning environment for material constitutive relations referred to as VizCoRe is presented. Visualization examples of two constitutive relations, the linear elastic with von Mises failure criteria and the Modified Cam Clay (MCC) are shown. These include two- and three-dimensional renderings of stress states and paths and yield and failure surfaces. In addition, the environment allows for the visualization of the implicit integration algorithm used for the numerical integration of both constitutive models. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Back analysis of model parameters in geotechnical engineering by means of soft computing

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 14 2003
B. Pichler
Abstract In this paper, a parameter identification (PI) method for determination of unknown model parameters in geotechnical engineering is proposed. It is based on measurement data provided by the construction site. Model parameters for finite element (FE) analyses are identified such that the results of these calculations agree with the available measurement data as well as possible. For determination of the unknown model parameters, use of an artificial neural network (ANN) is proposed. The network is trained to approximate the results of FE simulations. A genetic algorithm (GA) uses the trained ANN to provide an estimate of optimal model parameters which, finally, has to be assessed by an additional FE analysis. The presented mode of PI renders back analysis of model parameters feasible even for large-scale models as used in geotechnical engineering. The advantages of theoretical developments concerning both the structure and the training of the ANN are illustrated by the identification of material properties from experimental data. Finally, the performance of the proposed PI method is demonstrated by two problems taken from geotechnical engineering. The impact of back analysis on the actual construction process is outlined. Copyright © 2003 John Wiley & Sons, Ltd. [source]

Ground-penetrating radar survey to map the location of buried structures under two churches

ARCHAEOLOGICAL PROSPECTION, Issue 4 2002
Giovanni LeucciArticle first published online: 21 NOV 200
Abstract The range of ground-penetrating-radar (GPR) applications is very wide and diverse. Ground-penetrating radar provides high-resolution continuous profiles, and it has been used in various fields such as environmental, geology, geotechnical engineering, archaeology, etc. Two surveys with GPR were undertaken inside two churches (the church of St Oronzo and the church of Immacolata) at Novoli village, located a few kilometres northwest of Lecce (Italy). The purpose of the two surveys was to obtain information about the existence of ancient structures beneath the two churches. No document or writing exists to confirm the presence of structures under the two churches. However, there are several oral testimonies handed down over the centuries that suggest the presence of these ancient structures. Both surveys were carried out using a GSSI Sir System2, incorporating 500 MHz centre frequency antenna. The GPR time slices were constructed from closely spaced parallel profiles. The time slices, computed from averaging radar reflections over vertical time windows several nanoseconds thick, are used to map subsoil features associated with the structures, probably of anthropogenic origin. To facilitate the interpretation of the results, a three-dimensional image was constructed using closely spaced parallel profiles, which are linearly interpolated. Copyright © 2002 John Wiley & Sons, Ltd. [source]