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Würzburg, Germany

Raithel M.,Kempfert Geotechnik GmbH | Kuster V.,IAG | Alexiew D.,Huesker Synthetic GmbH
Geotechnik | Year: 2013

Foundation systems using geotextile encased columns for earth structures (e.g. embankments) on soft subsoil with a low bearing capacity were established in geotechnical engineering about 20 years ago and today are state-of-the-art in Germany. The system offers a geotechnical solution for foundations even in highly deformable soils of extremely low shear strength, in which traditional soil improvement techniques reach their limit of practicability. This paper gives a description of the system of geotextile encased columns, of design and construction procedures and in particular of the results of long-term measurements. Further information is given on ongoing developments of the system corresponding to technical and economical requirements of major geotechnical projects as well as further application options. Copyright © 2013 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.

The axial pile resistance of open ended piles like open ended pipe piles, H-piles and double H-piles can be calculated after the recommendations of EA-Pfähle or EAU. A comparison of these calculation methods shows that the results differ from each other. This can cause uncertainties to the users which are following the recommendations. The paper harmonizes both calculation methods. Based on a database with dynamic and static pile resistance results, new empirical values for the calculation of bearing capacity are derived using statistical methods. Furthermore the soil plugging effect is considered in a simplified method depending on the pile diameter. The validation of the new calculation method with statistic methods is based on the amount of pile tests in the database and can be confirmed. Therefore, this method is suggested for application in both national recommendations. This paper closes with a parameter study and comparison calculations. © Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.

Raithel M.,Kempfert Geotechnik GmbH | Werner S.,Kempfert Geotechnik GmbH | Kuster V.,Josef Mobius Bau AG | Alexiew D.,Huesker Synthetic GmbH
Bautechnik | Year: 2011

The foundation system Geotextile Encased Columns (GEC) for embankments on soft subsoil started in Germany about 15 years ago and has become state-of-the-art. The recent German Code for design of geosynthetic reinforced soil systems (EBGEO 2010) of the German Geotechnical Society comprises design and dimensioning procedures and provides useful recommendations regarding concepts and construction as well. Based on the permanently increasing practical experience, it seems that the system has higher bearing resources than formally calculated. A 1: 1 field test was designed "on the edge" in order to provoke a limit state of the system and to identify its "upper limits". The most important first test results are shown, evaluated and commented and possible tendencies for modifications regarding some design and calculation aspects are explained. Copyright © 2011 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.

In the course of the expansion of the existing RheinkraftwerkIffezheim (i.e. running-water power station in Iffezheim), a companionship of the EnBW Kraftwerke AG and EDF Electricité de France, three excavation pits are required to install the fifth bulb turbine: the uptstream excavation pit (entry), the main excavation pit (power plant) and the downstream excavation pit (siphon pipe and exit). All three excavation pits are in the middle of an artificial island which is connected to the existing power plant. The main excavation (dimensions 51 m to 36 m, excavation depth appr. 34 m) is an oval (ellipsoidal) excavation pit without struts and rear anchorage of the pit walls. Because of the shape of the main excavation pit and the asymmetric geometric and load boundary conditions, a complex three-dimensional numeric model for the calculations was needed which was able to take into account the special structural behavior of the excavation pit appropriately. © 2011 Ernst & Sohn Verlag für Architektur und technische Wissenschaften GmbH & Co. KG, Berlin.

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