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Item type:Publication, Access status: with files , Comparison of the three main multifluid extensions of the lattice Boltzmann method used for modeling unsaturated soilsThe complex behavior of unsaturated soils is closely linked to the distribution of the two fluids, water and air, within their pore space. Pore-scale modeling of the fluid distribution can therefore be beneficial for advancing unsaturated soil mechanics. The Lattice Boltzmann Method (LBM) is a popular choice for such modeling, due to its simplicity and computational efficiency. Several extensions of the single-phase LBM have been proposed to model multifluid systems; however, there is no clear consensus on which formulation is most suitable for simulations of unsaturated soils. The objective of this study is to compare the three multifluid approaches commonly used in the field: multiphase Shan–Chen (MPSC), multi-component Shan–Chen (MCSC), and He–Chen–Zhang (HCZ). All three approaches are implemented within an in-house LBM code and are carefully calibrated to ensure consistent interfacial properties. The methods are then applied to simulate drainage and imbibition in a two-dimensional granular packing. Their performance is evaluated in terms of their ability to reproduce pore-scale fluid distributions as well as their computational efficiency. A simple physical model is additionally used to provide qualitative verification of the simulated fluid configurations. The results indicate that, for the capillarity-dominated, quasi-static simulations examined in this study, the MPSC approach provides the most favorable balance between accuracy and computational efficiency.Publicationtype: Journal Article19 20 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Advanced hypoplastic contact modelling of field tests for tension piles in layered soilsConventional Coulomb friction models often fail to reproduce the complete non-linear load–displacement response of soil–pile interfaces, particularly during unloading–reloading sequences. Advanced hypoplastic contact formulations address these limitations by capturing pressure dependency (barotropy), density dependency (pyknotropy), and surface roughness effects using the same constitutive parameter set as the surrounding soil continuum. This study presents the first three-dimensional back-analysis of a hypoplastic contact model benchmarked against full-scale tensile load tests on steel H-piles in a complex, 23-layer stratified soil profile. The methodology establishes a physically consistent calibration framework where the interface roughness parameter is derived directly from torsional interface shear tests on pile-specific steel, rather than empirical estimation. These same contact formulations are subsequently applied to simulate the laboratory tests, ensuring consistency between calibration and field-scale prediction. The model accurately reproduces the field response and reduces the root mean square error (RMSE) by 71% relative to the Coulomb model, capturing hysteretic loops that simplified models miss. A parametric sensitivity analysis identifies interface roughness and pile circumference as the dominant capacity drivers, while relative density and in-situ earth pressure exert a moderate influence. The results demonstrate that physically based contact formulations are essential for accurate pile-soil interaction modelling in complex profiles, enabling more reliable and economical foundation design.Publicationtype: Journal Article16 19 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Large deformation simulations of structure–soil-interaction in anisotropic fine-grained soils(Elsevier, 2025-12-01); ; ; ; Structure–soil-interaction in fine-grained soils is strongly influenced by rate dependency, anisotropy, and overconsolidation effects. While advanced constitutive models such as Anisotropic Visco-Intergranular Strain Anisotropy (AVISA) can capture the fine-grained soil effects, the model application is typically limited to small strain problems due to numerical challenges. This study presents the first successful implementation of the AVISA model within explicit simulations in Abaqus, enabling robust modelling of large deformation problems in fine-grained soils. Two previously underexplored applications are investigated: (i) the stability assessment of a Liebherr LTR 1220 telescopic crawler crane during dynamic uppercarriage rotation under varying overconsolidation ratios (OCR), and (ii) the penetration process of an open-ended tubular pile in anisotropic, overconsolidated clay, focusing on penetration resistance and the evolution of stress and void ratio. Both problems are simulated using the Lagrangian FEM and the Coupled Eulerian–Lagrangian (CEL) approach and are qualitatively compared to available field data. The results demonstrate the capability of the AVISA model to address complex large deformation geotechnical problems realistically. The proposed approach provides new insights and practical tools for modelling structure–soil-interaction in situations where conventional methods often fail.Publicationtype: Journal Article18 21 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Implementation of linear strain elements for image-based Finite Element Analysis of cemented natural sandMesoscopic approaches in material science aim to conceive multiphase materials as compositions of constituent phases, rather than homogenized media. X-ray Computed Tomography is a powerful tool that provides full field information of composites’ structure in the form of three-dimensional images. Image analysis combined with computational geometry concepts permit the transition from voxel images to adapted unstructured tetrahedral meshes, a conversion that delivers important computational benefits of image-based numerical simulations. The current article focuses on the case of cemented natural granular material of two cement saturation degrees. Actual cylindrical samples are scanned and reconstructed in the form of digital volumes. Image artefacts impede reliable particle segmentation. A novel image filter based on domain cylindrical decomposition and histogram compatibility enforcement is applied to alleviate the bias. The conversion of voxel images to quadratic tetrahedral meshes is proposed to facilitate accurate image-based numerical analysis. Localization of stresses is evident in the upgraded linear strain element configuration, but missing from that of constant strain element. The display of stress results and supplementary statistical analysis suggest that the granular skeleton sustains the load by forming intergranular stress channeling, while the cement matrix is partially activated at regions of granular contact to aid the stress flow.Publicationtype: Journal Article20 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Discrepancies between element tests and large-scale LDFE simulations: A case study on anchor kinematics during installation in clay(2023-11); ; Harsh offshore conditions impose significant challenges to the design of floating offshore wind turbines (FOWTs). In particular anchoring systems face many uncertainties due to the unknown soil response and post-installation soil state. This study investigates the drag embedment anchor (DEA) installation in fine-grained soil through numerical simulations, employing large-deformation finite element (LDFE) analyses using the CEL method and visco-hypoplastic constitutive equations. Three parameter sets for kaolin clay were determined, which show excellent agreement to experimental data (MPE <6%). The study analyses the variation of the viscosity index Iv, determined by three acknowledged methods (oedometer test, triaxial test, and liquid limit). Despite element tests revealing minimal differences, large-scale LDFE simulations of DEA installation with varying Iv values significantly diverge. However, the viscosity index does not impact the relationship between anchor rotation and penetration. These findings emphasise the necessity for a comprehensive understanding of anchor-soil interaction and the limitations of numerical simulations lacking physical validation. This study contributes to the reliable design and installation of FOWTs by spreading awareness on the complex DEA kinematics in fine-grained soils and showcasing the importance of careful parameter calibration for numerical frameworks.Publicationtype: Journal Article10 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Investigation of the load sustaining micro mechanisms of cemented sand using the mesoscale FEM approachWhile the mechanics of cemented granular material have already been approached by means of constitutive modeling, the capacity of introducing the precise internal structure of multiphase media in numerical simulations offers an alternative perspective of investigation. In specific, means of X-ray computed tomography are able to quantify the internal irregular geometry of the composite material in the form of three-dimensional images. Image analysis can be applied in order to distinguish the topology of each material phase and advanced meshing techniques are able to form a twin meshed domain. The current paper deals with the quantitative description of the morphology of small cemented sand samples, the application of developed image analysis algorithms to treat imaging artefacts (mainly due to beam hardening), the equivalent mesh generation via the image adapted meshing technique and the numerical testing using the Finite Element Method. Four samples are imaged, meshed and numerically tested in uniaxial compression; the mesoscale finite element simulations are able to display the intergranular stress transmission chains. A statistical analysis of the load carried by the granular skeleton provides evidence of the influence of the cementation degree and the compaction of the aggregates on the uniformity of the stress distribution.Publicationtype: Journal Article33 100 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Coupled Eulerian Lagrangian based numerical modelling of vibro-compaction with model vibrator(2020-07); The use of field experience and empirical relations for the design of a vibro-compaction encourages the development of the understanding of vibratory compaction for granular material. Field measurements are difficult to conduct in homogeneous loose sands, and there is a lack of adequate control of the test conditions in the field. Hence, a model vibrator was fabricated to perform 1g vibro-compaction model tests. The effectiveness was evaluated in terms of cone penetration tests before and after compaction. The 1g model test results suggested that the degree and radial extent of compaction increased with frequency for the considered sand for a fixed vibrator mass and eccentricity. A coupled Eulerian Lagrangian-based numerical model simulating the 1g model tests was created, and the results from the physical model tests and numerical simulations were found to be in good agreement. Following this validation, the numerical framework was used to study the influence of a range of frequencies and the nature of the sand on the degree and extent of compaction. The numerical simulations were found to not only provide spatial and temporal compaction analysis freedom but also to serve as a substitute for laborious and time-consuming physical model tests.Publicationtype: Journal Article81 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Numerical and experimental analysis of the extraction mechanism of an anchor plate embedded in saturated sand(2019-07); ; ; Floating offshore structures can be founded on submerged foundations such as anchor plates. Their extraction resistance is of major importance during and at the end of the lifetime cycle. During their lifetime cycle, the foundation is suspended to complex loading conditions due to waves, tidal currents and wind loads and its resistance has to be known. At the end of the lifetime cycle, the anchor plates have to be removed from the seabed. The extraction resistance of the anchors is thereby a lot higher than the sum of its self-weight and hydrostatic and earth pressure. When the anchor plate is moved, the volume underneath increases. This leads to a suction until inflowing pore water fills the newly created volume. In order to investigate this effect, an experimental study at model scale with a displacement-driven extraction is performed. Pore pressure measurements are carried out at various locations in the soil body and underneath the plate. The soil movement is tracked with the particle image velocimetry method (PIV). In the conducted experiments different extraction velocities are considered to investigate its effect on the extraction resistance. Numerical investigations with unresolved coupled CFD-DEM are carried out and validated against the experimental results.Publicationtype: Journal Article217 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Large scale parallelisation of the material point method with multiple GPUs(2018-09); The material point method (MPM), which is a combination of the finite element and meshfree methods, suffers from significant computational workload due to the fine mesh required in spite of its advantages in simulating large deformations. This paper presents a parallel computing strategy for the MPM with multiple Graphics Processing Units (GPUs) to boost the method's computational efficiency in large scale problems. Domain decomposition method is used to split the workload over subdomains onto a number of GPUs. Communication between the subdomains is implemented by the data transfer between GPUs and random access memory. On each GPU the MPM algorithm is parallelised over nodes or particles. Benchmark problems of slurry runout and surface pipe penetration are analysed to quantify the speedup of the multiple-GPU parallel simulations over the sequential counterparts on the central processing unit. The maximum speedup with 1 GPU is 84 and increases to ∼1280 using 16 GPUs.Publicationtype: Journal Article153 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Numerical model to predict the displacement of piles under cyclic lateral loading using a new hypoplastic spring element(2018-09); ; A numerical model to predict the displacement of piles under cyclic lateral loading using a new type of spring element is demonstrated. The formulation of the numerical model is based on the subgrade reaction method and allows for modelling of a limited number of cycles. To accurately represent the soil behaviour, the spring elements are established on a hypoplastic formulation. Thereby, important soil properties like barotropy, pycnotropy and directionality are captured. Input parameters are determined by laboratory tests and correlations from literature. Performance of the new approach is demonstrated and the results are compared to Finite-Element-Analyses and current standards.Publicationtype: Journal Article305