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    Adhesion between clay and steel due to rotational shearing and normal separation
    Adhesion between clay and steel surfaces plays a critical role in governing clogging, tool wear, and interface resistance in tunnelling and offshore applications. Despite its significance, the underlying mechanisms of adhesion are not yet fully understood. This research proposal aims to systematically investigate clay-steel interfacial adhesion under mixed-mode loading conditions and to develop a numerical framework capable of realistically capturing the associated contact complexities. To achieve this, controlled laboratory experiments will be carried out using a custom-built apparatus designed to apply rotational shear and normal separation simultaneously, while measuring torque, force, and pore pressures at the steel-clay interface. To capture the experimental response, a hydro-mechanical interface model will be formulated by extending classical traction-separation laws to incorporate suction and drainage effects, thereby capturing the rate- and history-dependent behavior of the interface. The developed model will subsequently be implemented within a finite element framework and validated against the experimental results. Finally, a set of parametric studies will be conducted to quantify the effects of contact time, separation and rotation rates, and loading paths on adhesive strength of clay. The overall objective is to establish a fundamental understanding of adhesion at clay-steel interfaces through integrated experimental and numerical approaches, thereby enabling improved prediction of clogging risks and soil detachment in geotechnical engineering practice.
      14
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    Experimental investigation of capillary collapse of partially saturated granular soils during saturation (2)
    The objective of the second project phase is to formulate a constitutive model for the capillary collapse of granular soils with bimodal porosity within a continuum mechanics framework. Capillary collapse is defined as an irreversible volumetric deformation triggered by an increase in the degree of saturation of unsaturated soils. This phenomenon is governed by several interacting factors, including irrigation conditions, the applied stress state, and the porosity of the soil. The ongoing first project phase has already provided an extensive experimental basis, ranging from macroscopic tests to particle-scale investigations. These studies have demonstrated that capillary collapse is strongly linked to soil water retention behaviour and to the imposed boundary conditions. In particular, the presence of porous lignite particles has been shown to influence the collapse mechanism. Therefore, evaluating soils with varying lignite contents is essential to capture the true extent of this effect. The main challenge now lies in developing a mathematical expression that integrates the governing factors and accurately predicts the magnitude of collapse. Achieving this will provide the foundation for predictive constitutive modelling. Using the comprehensive experimental dataset already available, the proposed work aims to derive, formulate, and validate a constitutive model that links bimodal porosity, water retention behaviour, and collapse mechanisms. This model will establish the basis for future computational applications and the extension of predictive tools in unsaturated soil mechanics.
      13
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    Drift of Profiles Penetrated Into Soils
    The research project comprehensively investigates the drift of profiles during soil penetration. The main objective is to understand the mechanisms and conditions under which profiles deviate during soil penetration. This includes the development of mechanical models that describes the drift depending on profile geometry, soil type, soil condition, and load history. Through numerical simulations and experimental investigations in the centrifuge, the relevant influencing factors will be identified and validated. The results will lead to practical recommendations for the design of profiles to ensure accurate and precise insertion. In summary, the project aims to create a deep understanding of the physical processes that influence the drift of profiles in the soil and to provide engineers with robust tools to ensure the positional and shape accuracy of profiles.
      26
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    Coupled hydromechanical behaviour of unsaturated soils via LBM-DEM simulations: analysis of effective stresses due to capillary bridges and moving particles
    Although most soils exist in the unsaturated state, usually the geotechnical calculations are done considering the saturated state, which means that the air in the pore space is neglected and thus also the capillary forces between the grains. In geotechnical engineering, the capillary cohesion is usually not considered because of two factors: it is difficult to calculate it and also to assure that the water content of the soil will stay constant. In order to enhance design tools and allow simulation of soils by a computer, numerical methods are employed. This research proposal intends to further develop a numerical method that is able to simulate those unsaturated soils in the particle and meso-scale at its first part. This tool will be able to resolve multiphase flow in granular media using the Lattice Boltzmann method (LBM) and track grain movement using Discrete Element Method (DEM). By observing the momentum exchange between all three phases, it is possible to observe what follows from it. The main objective of this research is to numerically visualize the hydromechanical behaviour of unsaturated soils. The mentioned numerical tool allows further investigations of how effective stresses and consequently stiffness and shear strength develop in unsaturated media, and how soil properties and grain movement influence this behaviour. Multiple numerical simulations will be carried out while varying soil parameters and grain characteristics in order to observe their influence on effective stresses and shear strength.
      15
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    On the load-bearing behaviour of tension piles
    The research project comprehensively investigates the interaction between tension steel piles and surrounding soil. The main goal is to explain the significant discrepancies between the expected and actually measured load-bearing capacity of tension piles. Through detailed laboratory experiments and simulations, the frictional behaviour at the contact surface between pile and soil is examined as a function of factors such as surface texture and soil type. With the help of computed tomography, the processes can be observed on the smallest scale of individual soil particles. Further goals are to gain a better understanding of the influence of thinly inter-layered soils as well as the pile installation method on the later load-bearing capacity. In addition, innovative approaches such as bio-inspired surface structures will be tested for their potential to improve the load-bearing capacity. The research findings will help to better understand the complexity of the pile-soil interaction and develop more realistic calculation models and optimized solutions for the design and construction of tension piles.
      26
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    Wheel-Soil-Interaction under Extreme Conditions
    Anders als bei der Fahrzeugmobilität auf der Straße bildet die Interaktion zwischen Rädern und Boden einen Eckpfeiler, der die Leistung und Sicherheit von Geländefahrzeugen maßgeblich beeinflusst. Von Baustellen und landwirtschaftlichen Feldern bis hin zu Offroad-Strecken und außerirdischen Landschaften: Die Dynamik der Boden-Rad-Interaktion beeinflusst die Traktion, Manövrierfähigkeit, Energieeffizienz und Gesamtstabilität des Fahrzeugs. Die Bewegung der Räder auf lockerem, körnigem Boden ist aufgrund des unterschiedlichen Schlupfverhaltens der Räder anders als bei Straßenfahrzeugen. Aus diesem Grund sind herkömmliche kinematikbasierte Lenkmodelle für Straßenfahrzeuge nicht auf Geländefahrzeuge anwendbar, insbesondere wenn sie sich über lockeren Boden bewegen. Ferngesteuerte Fahrzeuge (ROVs) erweitern die Dimensionen der Boden-Rad-Interaktion weiter. ROVs sind wichtige Werkzeuge für die Erkundung gefährlicher, unzugänglicher oder außerirdischer Umgebungen. Diese Fahrzeuge werden oft aus der Ferne betrieben und ermöglichen so die Erkundung und Datenerfassung an Orten, an denen der direkte Zugang für den Menschen schwierig oder gefährlich ist. Im Kontext der Boden-Rad-Interaktion erhält die Herausforderung, die Traktion aufrechtzuerhalten, Schlupf zu verhindern und Stabilität zu gewährleisten, eine neue Dimension, wenn ROVs zum Manövrieren unter extremen Bedingungen wie abschüssigem Gelände eingesetzt werden oder unter Wasser. In solchen Fällen spielen Steuerungsstrategien eine entscheidende Rolle bei der Optimierung des Fahrzeugs Verhalten als Reaktion auf die dynamische Boden-Rad-Interaktion. Durch Echtzeiterfassung, Datenverarbeitung und Betätigung können Steuerungssysteme Parameter wie Drehmomentverteilung und Lenkung anpassen Winkel und Bremsen, um Schlupf zu mildern, die Traktion zu verbessern und ein Umkippen zu verhindern. Die Kernidee dieses Forschungsvorhabens besteht darin, ein numerisches Modell zu entwickeln, das die genaue Kinematik eines Rovers, der auf losem Sand fährt, simuliert und Erkenntnisse über das lose Rad gewinnt Sandinteraktionen, um eine heuristisch-basierte Traktionskontrollstrategie (TCS) zu entwickeln. Die erfolgreiche Implementierung dieses TCS im numerischen Modell kann zur Verbesserung der Fähigkeiten von ROVs unter extremen Bedingungen beitragen, ohne dass sehr teure physische Prototypen erforderlich sind.
      5
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      16
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    Load-bearing behavior and interaction of rigid inclusion systems with granular load transfer platforms
    Rigid inclusions, are a relatively new method for soil improvement in Germany. An essential difference between rigid inclusions and conventional pile foundations is the load transfer platform (LTP) above the columns. The columns, the soil between the columns and the LTP interact and form a combined overall system which determines the load bearing behavior. The research project is focused on the type of wet mortar column. After the penetration of the partial or full displacement auger the concrete is injected. The diameter of the columns is usually approx. 20 to 40 cm. They are installed in a grid with a centre to centre distance of 3D to 5D. The load-bearing behavior of rigid inclusion systems is not yet fully understood and the models on which the design is based are simplified approaches. The influence of a change in the soil state parameters due to the grid-shaped installation process is not yet quantified. Furthermore, the influence of cyclic loading on the load transfer and the arching effect in the LTP has not been sufficiently researched. The main objective of the research project is therefore to clarify the load-bearing behavior of rigid inclusion systems, taking the installation effect, the group effect and the interaction between soil, column, load transfer layer and foundation under static monotonic and cyclic loading into account. For this purpose, numerical simulations are carried out, which are supplemented and validated by model tests. For the numerical calculations, continuum models are used. The corresponding equations are solved with FEM. For this purpose, the CEL approach is applied, which has proven itself in the preliminary investigations for the simulation of the drilling process.
      44
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    Closed-loop control of a nonlinear vibrator-profile system penetrating a heterogeneous ground
    This research project aims to develop a nonlinear closed-loop controller to optimize the vibrodriving process, minimizing the installation time and the vibrations transmitted to the surroundings. Therefore, a simplified nonlinear mechanical model describing the vibrator-pile-soil interaction will be developed and simulated. From the simplified mechanical model, a controller is derived and tested in simulation. The construction of an experimental set-up representing the vibrodriving process is planned. In the experimental set-up, the derived controller will be tested for different soil conditions and pile profiles. Afterward, numerical simulations will be conducted to assess the extension of the results in the model to real-life scenarios, and an extra degree of freedom considering the control of the eccentric moment is considered.
      56
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    Bearing capacity increase of geotechnical structures through shear band enhancement
    The proposed research project will investigate the ultimate limit state of geotechnical structures concerning the increase in limit load. Shear bands that will develop in the soil are of main interest. A new approach to limit load increase of geotechnical structures will be examined: The enhancement of shear bands. Based on the concept of one critical failure mechanism and the corresponding limit load, the limit load can be increased, if the critical failure mechanism is prohibited through targeted soil reinforcement. Numerical simulations will reveal the shear bands and limit loads of several geotechnical structures. A method to automatically simulate the shear band enhancement will be developed, based on already developed methods for numerical optimization of geotechnical structures within the serviceability state. The increase of limit load can therefore be determined as well as the loads acting on the reinforcing material. Following 1g-model tests with shear band enhancement will be conducted. Preliminary tests determine suitable methods and materials for the reinforcement of shear bands in the model scale. The insights of the 1g model tests will be extended to ng-model tests in a geotechnical centrifuge. Therefore the applicability of shear band enhancement for the increase of limit load will be verified. Transient loads and the practical implementation will be examined during a second project phase.
      105