Three Dimensional Wave Propagation due to Pile Driving

A very economical and efficient method to construct pile foundations or sheet walls is given by the driving of the pile itself in the case of prefabricated piles or of the steel-sheet pipe for concrete piles in situ and also by the driving of the sheet piles in the case of sheet walls. In spite of its efficiency this method underlies, because of environment protection reasons to certain restrictions that concern the influence of the produced shock waves during the driving procedure to neighboring buildings and constructions. For the theoretical calculation of this influence at first the free-field response of the ground due to the propagated shock waves will be required. The source wave is generally of transient nature. The authors deal in this contribution with the theoretical calculation of free-field magnitudes for an elastic homogeneous half-space as an adequate model for an idealized ground

Lagrange-Euler Formulierungen in der Bodenmechanik

Bodenmechanische und geotechnische Problemstellungen werden häufig durch große Materialverformungen und andere damit einhergehende Phänomene gekennzeichnet. Bei deren Modellierung stoßen die klassische Bodenmechanik und die traditionelle Finite Elemente Methode basierend auf der Lagrange Formulierung an ihre Grenzen. In dem Beitrag werden die kontinuumsmechanischen Grundlagen einer verallgemeinerten Lagrange-Euler Formulierung vorgestellt. Anschließend werden ihre unterschiedlichen Ausprägungen im Rahmen der numerischen Umsetzung anhand von Anwendungsbeispielen diskutiert sowie das Potential dieser Simulationsmethoden in der Bodenmechanik und Geotechnik aufgezeigt.DFG, 76838227, Numerische Modellierung der Herstellung von Rüttelinjektionspfähle

Stone Column Ground Improvement Against Liquefaction for the Preveza-Aktio Immersed Tunnel

The construction of the road fixed-link crossing between Preveza and Aktio on the north-western coast of Greece has recently been completed. The project consists of an immersed single-tube tunnel under the strait and two cut-and-cover tunnels at the ends of the immersed part. The immersed section is constructed of eight precast rectangular concrete elements placed on the sea bottom at a depth of 25 m. The site is characterized by high seismicity. Foundation soil consists of Holocene marine sediments comprising irregular layers of sands, silts and clays that extend to great depth in the central part of the strait. Along the entire tunnel alignment the silty sands and sandy silts of the top layers are classified as potentially liquefiable due to their low density. Soil improvement in the form of stone columns has been carried out below the tunnel foundation for reducing risk from liquefaction. The soil conditions and the seismic input parameters are presented and an overview of the extensive dynamic laboratory testing program conducted is given. The seismic site response analyses performed for determining the depth of ground improvement are summarized. The design of the stone columns as well as a practical method for estimating the stiffness of the composite soil are described

Geotechnical and Environmental Consideration by Planning and Construction of the Transportation Infrastructure in the Centre of Berlin

Since the mid of the nineties in the City of Berlin there have been built underground installations, i.e. railway and street tunnels as well as foundations deep embedded in the groundwater, with some extraordinary measures. The surface area of all tunnel constructions of the VZBProject (inner city traffic tunnels in Berlin) amounts to approx. 240,000 square meters. The excavation pits for the tunnel structures have depths of more than 20 meters and widths of more than 100 meters. All this projects lead in the mid nineties to the characterization of the City of Berlin as Europe`s biggest construction site. A general overview of the transportation infrastructure project will be given here. A number of technical problems had to be resolved and new strategies devised at the planning stage because of the geotechnical and hydrogeological conditions in the central area of Berlin, the environmental requirements concerning groundwater conditions, and interaction with the surrounding green area and the nearby existing buildings. Several methods of tunnelling constructions in cohesionless soils with high ground water level were applied, such as caissons, shield driven tunnels and trough-type excavations (cut-and-cover tunnels). The geotechnical and hydrogeological conditions will be presented and the planning and realization of the tunnelling construction methods will be explained in the paper. Quality assurance was an important issue of the project and included an extensive monitoring system to ensure the quality of the constructions and to control the prior design and calculations. The impact of the project on the urban life and on the environment wouldn`t be minimized without a sophisticated project and ground water management. A very extensive measurement program in the frame of the quality assurance and geotechnical observation method was performed. It consisted of tension loading tests of single piles and groups of piles as well as measurements of anchor forces, wall deformations, uplift and leak water. Some data of monitoring are presented and discussed in this case history report

Management of large construction projects and risk minimization by web-based software technology

Risk and Reliability in Geotechnical Engineerin

Theory and Numerical Modeling of Geomechanical Multi-material Flow

Multi-material flow describes a situation where several distinct materials separated by sharp material interfaces undergo large deformations. The research presented in this paper addresses a particular class of multi-material flow situations encountered in geomechanics and geotechnical engineering which is characterized by a complex coupled behavior of saturated granular material as well as by a hierarchy of distinct spatial scales. Examples include geotechnical installation processes, liquefaction-induced soil failure, and debris flow. The most attractive numerical approaches to solve such problems use variants of arbitrary Lagrangian–Eulerian descriptions allowing interfaces and free surfaces to flow through the computational mesh. Mesh elements cut by interfaces (multi-material elements) necessarily arise which contain a heterogeneous mixture of two or more materials. The heterogeneous mixture is represented as an effective single-phase material using mixture theory. The paper outlines the specific three-scale mixture theory developed by the authors and the MMALE numerical method to model and simulate geomechanical multi-material flow. In contrast to traditional flow models which consider the motion of multiple single-phase materials or single multi-phase mixture, the present research succeeds in incorporating both the coupled behavior of saturated granular material and its interaction with other (pure) materials.DFG, 76838227, Numerische Modellierung der Herstellung von Rüttelinjektionspfähle