Ground Improvement by Deep Vibratory Methods

Vibro compaction and vibro stone columns are the two dynamic methods of soil improvement most commonly used worldwide. These methods have been developed over almost eighty years and are now of unrivalled importance as modern foundation measures. Vibro compaction works on granular soils by densification, and vibro stone columns are used to displace and reinforce fine-grained and cohesive soils by introducing inert material. This second edition includes also a chapter on vibro concrete columns constructed with almost identical depth vibrators. These small diameter concrete piles are increasingly used as ground improvement methods for moderately loaded large spread foundations, although the original soil characteristics are only marginally improved. This practical guide for professional geotechnical engineers and graduate students systematically covers the theoretical basis and design principles behind the methods, the equipment used during their execution, and state of the art procedures for quality assurance and data acquisition. All the chapters are updated in line with recent developments and improvements in the methods and equipment. Fresh case studies from around the world illustrate the wide range of possible applications. The book concludes with variations to methods, evaluates the economic and environmental benefits of the methods, and gives contractual guidance

Regulation of NGN: Structural Separation, Access Regulation, or No Regulation at All?

Since the introduction of Next Generation Networks (NGNs) by telecommunication network operators, national regulators have begun to adapt their access regulation regimes to the new technological conditions. The regulatory reactions gravitate towards three distinct regulatory trajectories: unregulated competition, access regulation, and structural separation. We first analyze the extent of market power in access Networks in NGNs from a technological perspective. Second, we use case studies to identify patterns between technological and market conditions and regulators' reactions in selected countries. We find that market power in the access network is likely to prevail. Regulatory reactions differ with the extent of infrastructure competition and the regulators position in the trade-off between promoting investment and protecting competition.Next Generation Network, deregulation, access regulation, structural separation

Regulation of NGN: Structural Separation, Access Regulation, or No Regulation at All?

Since the introduction of Next Generation Networks (NGNs) by telecommunication network operators, national regulators have begun to adapt their access regulation regimes to the new technological conditions. The regulatory reactions gravitate towards three distinct regulatory trajectories: unregulated competition, access regulation, and structural separation. We first analyze the extent of market power in access Networks in NGNs from a technological perspective. Second, we use case studies to identify patterns between technological and market conditions and regulators' reactions in selected countries. We find that market power in the access network is likely to prevail. Regulatory reactions differ with the extent of infrastructure competition and the regulators position in the trade-off between promoting investment and protecting competitionNext Generation Network, deregulation, access regulation, structural separation.

Ground Improvement by Deep Vibratory Methods

Vibro compaction and vibro stone columns are the two dynamic methods of soil improvement most commonly used worldwide. These methods have been developed over almost eighty years and are now of unrivalled importance as modern foundation measures. Vibro compaction works on granular soils by densification, and vibro stone columns are used to displace and reinforce fine-grained and cohesive soils by introducing inert material. This second edition includes also a chapter on vibro concrete columns constructed with almost identical depth vibrators. These small diameter concrete piles are increasingly used as ground improvement methods for moderately loaded large spread foundations, although the original soil characteristics are only marginally improved. This practical guide for professional geotechnical engineers and graduate students systematically covers the theoretical basis and design principles behind the methods, the equipment used during their execution, and state of the art procedures for quality assurance and data acquisition. All the chapters are updated in line with recent developments and improvements in the methods and equipment. Fresh case studies from around the world illustrate the wide range of possible applications. The book concludes with variations to methods, evaluates the economic and environmental benefits of the methods, and gives contractual guidance

Genehmigungs- und Zulassungsvoraussetzungen von Bodenmischsäulen

Dieser Aufsatz ist Teil des folgenden Sammelbandes: Innovationen im Spezialtiefbau : Fachseminar am 05. Dezember 2013 an der Technischen Universität Berlin. – Hrsg.: Bernd Kochendörfer. - (Bauwirtschaft und Baubetrieb : Berichte ; 2). – Berlin: Universitätsverlag der TU Berlin, 2013 ISBN 978-3-7983-2663-7 (print) ISBN 978-3-7983-2664-4 (online) URN urn:nbn:de:kobv:83-opus4-44427 [http://nbn-resolving.de/urn:nbn:de:kobv:83-opus4-44427]Vorliegender Beitrag behandelt die technischen und genehmigungsrechtlichen Belange beim Einsatz von sogenannten Bodenmischsäulen zur Verbesserung der Baugrundeigenschaften bzw. zur Herstellung eines lastab-tragenden Elementes im Untergrund

Experimentelle und numerische Untersuchungen zum Tragverhalten von Rüttelstopfsäulengruppen

Mit der vorliegenden Arbeit wird eine Kenntnislücke in Bezug auf die Anwendung des Rüttelstopfverfahrens zur Baugrundverbesserung unterhalb von räumlich begrenzten Lastflächen, beispielsweise Einzelfundamenten zur Gründung von Stützen oder Pfeilern, geschlossen. Im Rahmen der Untersuchungen wurden die Ergebnisse kleinmaßstäblicher Modellversuche dazu verwendet, Erkenntnisse über die Verteilung der vertikalen Belastung innerhalb einer Gruppe von Säulen zu gewinnen. Zur Ermittlung des Einflusses der Säulenherstellung auf den Spannungszustand und die Verformungseigenschaften im umgebenden Boden wurden Feldmessungen während der Herstellung von Rüttelstopfsäulen durchgeführt. Auf der Basis der Finiten Element Methode wurde ein Berechnungsmodell erstellt, welches das Lastabtragungsverhalten von Rüttelstopfsäulengruppen zutreffend beschreibt. Ein großmaßstäblicher und umfangreich instrumentierter in situ Versuch dient der Überprüfung der Modelle zur Berechnung des Tragverhaltens von Rüttelstopfsäulengruppen. Mit Hilfe des numerischen Modells wurden umfangreiche Parameterstudien zur Ermittlung des Last-Verformungsverhaltens von Rüttelstopfsäulengruppen unter vertikaler Belastung durchgeführt. Auf der Grundlage der Parameterstudien wurden Bemessungsdiagramme entwickelt, welche die Setzungsverbesserung durch den Einsatz der Baugrundverbesserung zeigen. Aus den Untersuchungen wurden Empfehlungen für die Dimensionierung von Rüttelstopfsäulengruppen abgeleitet. Mit Hilfe des numerischen Modells kann eine Optimierung der Säulenanordnung im Hinblick auf eine wirtschaftliche Gründung von Einzelfundamenten auf Rüttelstopfsäulen erfolgen.It is the prime objective of this thesis to describe the load deformation behaviour of a group of soil improvement stone columns under vertical load. All interactions participating in the overall load transfer mechanism are described in detail. The interactions result from specific circumstances of material and geometry. In general the three dimensional nature of the problem needs to be considered. Therefore model tests as well as in situ field trials are included in this study. By the process of introducing the stone column material into the ground its characteristics are modified. Measurements which accompany the execution of the field work monitor the qualitative and quantitative changes in the ground. Based upon these data a model is developed which allows the influence of the installation process to be considered in the calculations. By way of numerical calculations the influence of individual parameters of the overall system on the deformation behaviour is established. The model considers the structure in the three dimensional continuum. The kinematics of the problem in connection with constitutive law and boundary conditions lead to a boundary value problem which is resolved by the finite element method. The results of the field measurements together with those of the numerical calculations serve as basis for the analysis of the load carrying behaviour, clarification of the load transfer mechanism and establishing the interactions participating

Long-term cyclic triaxial tests with DEM simulations

Modeling the long-term performance of granular materials under cyclic loading conditions is still a challenge and a better understanding could provide a large benefit for the design of foundations. One typical application example are the foundations of wind turbines, for which the evolution of the soil mechanical behavior could lead to irreversible strain accumulation (with tilting and settlement) and dynamic resonance problems [1]. In this framework the Discrete Element Method [2] can provide useful information starting from a micromechanical point of view: it may allow engineers to increase their knowledge on the evolution of the mechanical behavior and to optimize the long-term design of these structures [3]. The present paper presents the capability of DEM to simulate a long-term cyclic drained triaxial test (up to 100,000 cycles). The results regard the progressive accumulation of plastic strain as function of the number of particles and the initial particles rearrangement. The influence of densification and contact orientation (anisotropy) in the evolution of the strength of the soil during the cyclic loading history is investigated

XMM observations of the high-redshift quasar RXJ1028.6-0844 at z=4.276: soft X-ray spectral flattening

We present results from a new XMM-Newton observation of the high-redshift quasar RXJ1028.6-0844 at a redshift of 4.276. The soft X-ray spectral flattening, as reported by a study with ASCA previously (Yuan et al. 2000, ApJ 545, 625), is confirmed to be present, however, with reduced column density when modelled by absorption. The inferred column density for absorption intrinsic to the quasar is 2.1(+0.4-0.3)x10^22 (cm^-2) for cold matter, and higher for ionised gas. The spectral flattening shows remarkable similarity with those of two similar objects, GB1428+4217 (Worsley et al. 2004, MNRAS 350, L67) and PMNJ0525-3343 (Worsley et al. 2004, MNRAS 350, 207). The results improve upon those obtained from a previous short-exposure observation for RXJ1028.6-0844 with XMM-Newton (Grupe et al. 2004, AJ 127, 1). A comparative study of the two XMM-Newton observations reveals a change in the power-law photon index from Gamma ~1.3 to 1.5 on timescales of about one year. A tentative excess emission feature in the rest-frame 5-10keV band is suggested, which is similar to that marginally suggested for GB1428+4217.Comment: 9 pages, accepted for publication in MNRAS; minor changes (added footnote commenting on the use of the F-test, added references

Regulation of NGN: Structural Separation, Access Regulation, or No Regulation at All?

Since the introduction of Next Generation Networks (NGNs) by telecommunication network operators, national regulators have begun to adapt their access regulation regimes to the new technological conditions. The regulatory reactions gravitate towards three distinct regulatory trajectories: unregulated competition, access regulation, and structural separation. We first analyze the extent of market power in access Networks in NGNs from a technological perspective. Second, we use case studies to identify patterns between technological and market conditions and regulators' reactions in selected countries. We find that market power in the access network is likely to prevail. Regulatory reactions differ with the extent of infrastructure competition and the regulators position in the trade-off between promoting investment and protecting competition

Regulation of NGN: Structural Separation, Access Regulation, or No Regulation at All?

Since the introduction of Next Generation Networks (NGNs) by telecommunication network operators, national regulators have begun to adapt their access regulation regimes to the new technological conditions. The regulatory reactions gravitate towards three distinct regulatory trajectories: unregulated competition, access regulation, and structural separation. We first analyze the extent of market power in access Networks in NGNs from a technological perspective. Second, we use case studies to identify patterns between technological and market conditions and regulators' reactions in selected countries. We find that market power in the access network is likely to prevail. Regulatory reactions differ with the extent of infrastructure competition and the regulators position in the trade-off between promoting investment and protecting competition