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Die Verdichtungsinjektion stellt ein Verfahren in der Geotechnik dar, bei dem der Baugrund durch Einpressen eines Mörtels mit hoher innerer Reibung verdichtet wird, ohne ihn aufzubrechen. Dieses Verfahren wird weithin verwendet zur Setzungskontrolle oder Erhöhung der Tragfähigkeit des Baugrunds unter neuen bzw. bestehenden Bauwerken.
Da die Injektion innerhalb des Bodens stattfindet, ist eine visuelle Beurteilung des Verdichtungserfolgs nicht möglich. Bisher beruht die Beurteilung bzw. Bewertung daher zumeist auf Erfahrungen. Ziel ist es somit mittels numerischer und experimenteller Untersuchungen eine Methode zu erschaffen, die es ermöglicht den Verdichtungserfolg nicht nur vorherzusagen sondern auch bezüglich der Materialparameter des Injektionsguts zu optimieren. Bezüglich der Numerik werden sowohl die grundsätzliche Eignung als auch die ersten notwendigen Anpassungen der impliziten "Material Point Method" zur Simulation einer Verdichtungsinjektion präsentiert. Für die experimentellen Untersuchungen wurde eigens ein Versuchsstand konstruiert, in dem es möglich ist, den Injektionsprozess an einer Glasscheibe zu beobachten und mittels digitaler Bildverarbeitung zu bewerten.
Compaction grouting involves the injection under high pressure of a highly viscous grout into the soil to displace and compact the surrounding soil without fracturing it. This ground improvement technique has been used widely for settlement control, increasing liquefaction resistance or bearing capacity of soil under new or existing structures. The work presented here aims to show some numerical and experimental investigations being carried out to understand the compaction mechanism and the soil-grout interaction, which is crucial for a successful usage of this technique.
To investigate compaction grouting in the laboratory under various stress conditions, a large-scale testing chamber has been developed. The grout was injected directly at the transparent vertical window of the chamber in order to investigate the possibility to monitor the injection process with a camera to measure the in-plane soil displacements and strains by means of the PIV technique. The other aim of this study is to develop a numerical model, which should be able to deal with large displacements and deformations and to simulate the change in shape of the distinct soil-grout interface solely as a result of the interaction between the injected grout and the surrounding soil. Based on these considerations, as a numerical technique, we employ the implicit Material Point Method based on a mixed formulation, which is implemented in the open source Kratos Multiphysics framework. In contrast to standard FE formulations, the usage of the MPM avoids both the numerical instability caused by extensive mesh distortion and the high computational costs of remeshing. The main results focus on the different evolution of the grout bulb inside the soil under various stress states.
Suction Bucket Jackets (SBJ) are found as a suitable alternative to driven piles for the support of foundations for offshore wind energy converters. In the case of jackets or multipods, a predominant vertical load is to be expected. The effect of such a tensile loading is the generation of suction in the soil inside the bucket which leads to an increment of tensile capacity. This paper aims to study the bearing behaviour of a suction foundation by taking into account how the soil permeability and the loading rate influence the foundation behaviour. Moreover, after submitting the structure to a storm load, the bearing capacity is studied again, in order to see the effect of such a load on the bucket's bearing behaviour. This study is carried out by means of Finite Element numerical simulations based on the formulation of Biot's equations combined with a constitutive model that reproduces the key aspects of cyclic soil behaviour in the frame of Generalized Plasticity.