Geotechnik最新文献

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Seit September 2021 entsteht in der Hamburger HafenCity, direkt am Oberhafenkanal, der Elbtower – ein ambitioniertes Bauprojekt auf engstem Raum. Auf dem 21.000 m² großen Baufeld an den Elbbrücken, unmittelbar neben dem S-Bahnhof, wurden bis Februar 2023 unter anspruchsvollen zeitlichen und technischen Rahmenbedingungen die Spezialtiefbauarbeiten durchgeführt. Zur Gründung des Hochhauses kamen 63 Großbohrpfähle mit einer beeindruckenden Tiefe von jeweils 83 Metern zum Einsatz. Darüber hinaus waren umfangreiche Sicherungsmaßnahmen für die Baugrube sowie komplexe Gründungen im Sockelbereich und für angrenzende Nebenbauwerke erforderlich. Die Baustelleneinrichtung musste dabei den parallelen Einsatz mehrerer Gewerke und Großgeräte ermöglichen – eine logistische Herausforderung, die das Baustellenteam kontinuierlich forderte. (Foto: ARGE Baugrube und Gründung Elbtower)

New aspects of ground treatment by deep vibration in design and execution

Ground treatment by depth vibrators has been applied for almost 100 years now in Germany and beyond and has made remarkable progress in this period. In its different technical variants is can be used in diverse ways for ground improvement. This development is obvious in the equipment and tooling employed as well as in the new technical regulations and standards for design and execution. The authors are presenting the latest developments in this field and are answering frequent questions that recently arose for specific aspects and details of ground treatment by deep vibration.

Practical experience in the application of the moisture condition value (MCV) for the construction of earthworks

Determining the MCV (Moisture Condition Value) allows the assessment of suitability of a cohesive soil for compaction. It is possible to determine within a short timespan whether the water content of the soil material is within the range of the optimum water content according to Proctor. If relevant, it is possible to determine the amount of water or binder to be added to the soil in order to achieve the desired water content. The method has been used for the construction of a test embankment for the Alpenrhein flood protection project (km 65 - 91). A “method compaction”-type of specification was used for this purpose, and the suitability of the earthworks-material for compaction was checked directly before compaction using the MCV. Moreover, the quantity of binder to be mixed into the soil was determined using the MCV value. The dry density of compacted materials was measured in order to evaluate the achieved quality of compaction. The results and experiences during construction of the test embankment are reported in this article, in particular with regard to the degree of compaction (D_Pr) and air void ratio (n_a).

In geotechnical engineering, various material models are available for numerical calculations, differing in formulation, applicability, and complexity. Selecting the right one is crucial for accurate results and high-quality predictions. Therefore, understanding the interactions between the material model's mathematical structure, input parameters, and the modelling process is essential. This paper investigates the impact and sensitivity of input parameters for the linear-elastic, ideal plastic Mohr-Coulomb Model, the elasto-plastic Hardening Soil Model, and the Soft Soil Model, focusing on tunnel cross-section deformations in challenging soft soils.Using the Finite Element Method Plaxis2D, a model accounting for relevant tunnelling boundary conditions is created. The three material models are calibrated based on simulated oedometric and triaxial tests to ensure comparable soil behaviour. The results demonstrate that the cross-sectional deformations determined from the two non-linear material models exhibit minimal discrepancy. For both, the heave of the invert, a consequence of tunnel excavation-induced unloading, represents the most significant deformation. The linear one proves to be inappropriate for modelling the given context due to an unrealistically large heave. The subsequent sensitivity analysis highlights the relevance of the soil unit weight γ, the stiffness $$ in the HSM and the swelling coefficient κ* and the Poisson's ratio ν_ur in the SSM.