TY - JOUR A1 - Farhat, Abbas A1 - Luu, Li-Hua A1 - Doghmane, Alexis A1 - Cuéllar, Pablo A1 - Benahmed, Nadia A1 - Wichtmann, Torsten A1 - Philippe, Pierre T1 - Micro and macro mechanical characterization of artificial cemented granular materials N2 - The focus of this study is the experimental characterization of cemented granular materials, with the aim of identifying the microscopic properties of the solid bonds and describing the extension to macroscopic mechanical strength of cemented samples.We chose to use artificially bonded granular materials, made of glass beads connected by solid paraffin bridges. The results of several sets of laboratory tests at different scales are presented and discussed. Micromechanical tests investigate the yield strength of single solid bonds between particles under traction, shearing, bending and torsion loading, as a function of variations in particle size, surface texture and binder content. Macro-scale tensile tests on cemented samples explore then the scale transition, including influence of confining walls through homothetic variations of the sample size. Despite the large statistical dispersion of the results, it was possible to derive and validate experimentally an analytical expression for micro tensile yield force as a function of the binder content, coordination number and grain diameter. In view of the data, an adhesive bond strength at the contact between bead and solid bond is deduced with very good accuracy and it is even reasonable to assume that the other threshold values (shear force, bending and torsion moments) are simply proportional to the tensile yield, thus providing a comprehensive 3D model of cemented bond. However, the considerable dispersion of the data at the sample scale prevents validation of the extended model for macroscopic yield stress. A final discussion examines the various factors that may explain intrinsic variability. By comparison with other more realistic systems studied in the literature in the context of bio-cementation, our artificial material nevertheless appears suitable for representing a cemented granular material. Being easy to implement, it could thus enable the calibration of discrete cohesion models for simulation of practical applications. KW - Cemented granular material KW - Micro-mechanical characterisation KW - Artificial soils KW - Yield tensile stress PY - 2024 DO - https://doi.org/10.1007/s10035-024-01426-2 SN - 1434-5021 VL - 26 IS - 3 SP - 1 EP - 20 PB - Springer CY - Berlin AN - OPUS4-63507 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kemmler, Samuel A1 - Rettinger, Christoph A1 - Rüde, Ulrich A1 - Cuéllar, Pablo A1 - Köstler, Harald T1 - Efficiency and scalability of fully-resolved fluid-particle simulations on heterogeneous CPU-GPU architectures N2 - Current supercomputers often have a heterogeneous architecture using both conventional Central Processing Units (CPUs) and Graphics Processing Units (GPUs). At the same time, numerical simulation tasks frequently involve multiphysics scenarios whose components run on different hardware due to multiple reasons, e.g., architectural requirements, pragmatism, etc. This leads naturally to a software design where different simulation modules are mapped to different subsystems of the heterogeneous architecture. We present a detailed performance analysis for such a hybrid four-way coupled simulation of a fully resolved particle-laden flow. The Eulerian representation of the flow utilizes GPUs, while the Lagrangian model for the particles runs on conventional CPUs. Two characteristic model situations involving dense and dilute particle systems are used as benchmark scenarios. First, a roofline model is employed to predict the node level performance and to show that the lattice-Boltzmann-based Eulerian fluid simulation reaches very good performance on a single GPU. Furthermore, the GPU-GPU communication for a large-scale Eulerian flow simulation results in only moderate slowdowns. This is due to the efficiency of the CUDA-aware MPI communication, combined with the use of communication hiding techniques. On 1024 A100 GPUs, an overall parallel efficiency of up to 71% is achieved. While the flow simulation has good performance characteristics, the integration of the stiff Lagrangian particle system requires frequent CPU-CPU communications that can become a bottleneck, especially when simulating the dense particle system. Additionally, special attention is paid to the CPU-GPU communication overhead since this is essential for coupling the particles to the flow simulation. However, thanks to our problem-aware co-partitioning, the CPU-GPU communication overhead is found to be negligible. As a lesson learned from this development, four criteria are postulated that a hybrid implementation must meet for the efficient use of heterogeneous supercomputers. KW - Discrete element method KW - Hybrid implementation KW - High-performance computing KW - Particulate flow KW - Lattice Boltzmann method PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-623958 DO - https://doi.org/10.1177/10943420241313385 SN - 1741-2846 SP - 1 EP - 19 PB - SAGE Publications AN - OPUS4-62395 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zinas, Orestis A1 - Papaioannou, Iason A1 - Schneider, Ronald A1 - Cuéllar, Pablo T1 - Multivariate Gaussian Process Regression for 3D site characterization from CPT and categorical borehole data N2 - Accurate prediction of subsurface stratigraphy and geotechnical properties, along with quantification of associated uncertainties, is essential for improving the design and assessment of geotechnical structures. Several studies have utilized indirect data from Cone Penetration Tests (CPTs) and employed statistical and Machine Learning methods to quantify the geological and geotechnical uncertainty. Incorporating direct borehole data can reduce uncertainties. This study proposes a computationally efficient multivariate Gaussian Process model that utilizes site-specific data and: (i) jointly models multiple categorical (USCS labels) and continuous CPT variables, (ii) learns a non-separable covariance structure leveraging the Linear Model of Coregionalization, and (iii) predicts a USCS based stratigraphy and CPT parameters at any location within the 3D domain. The results demonstrate that integrating geotechnical and geological data into a unified model yields more reliable predictions of subsurface stratification, enabling the parallel interpretation of both USCS classification and CPT profiles. Importantly, the model demonstrates its potential to integrate multiple variables from different sources and data types, contributing to the advancement of methodologies for the joint modeling of geotechnical, geological, and geophysical data. KW - Geotechnical site-characterization KW - Cone Penetration Tests KW - Stratigraphy prediction KW - Multivariate Gaussian process KW - Variational inference KW - Linear Model of Coregionalization PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-629456 DO - https://doi.org/10.1016/j.enggeo.2025.108052 SN - 1872-6917 VL - 352 SP - 1 EP - 19 PB - Elsevier B.V. AN - OPUS4-62945 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Benseghier, Z. A1 - Cuéllar, Pablo A1 - Luu, L.-H. A1 - Bonelli, S. A1 - Philippe, P. T1 - A parallel GPU-based computational framework for the micromechanical analysis of geotechnical and erosion problems N2 - This article deals with the relevance and practical feasibility of micromechanical simulations for their application to general geomechanical problems involving fluid-saturated granular assemblies, whether frictional or cohesive. A set of conceptual and numerical tools is here presented, advocating for a parallel computation using graphical processing units (GPUs) to treat large numbers of degrees of freedom with conventional Desktop computers. The fluid phase is here simulated with a particle-resolved approach in the frame of the Lattice Botzmann Method (LBM) while the granular solid phase is modelled as a collection of discrete particles from a Molecular Dynamics DEM perspective. The range of possible material behaviours for the solid granular phase is intended here to cover a broad spectrum from purely frictional to viscous cohesive materials with either brittle or transient debonding features. Specific details of the implementation and some validation cases are put forward. Finally, some exemplary applications in the fields of soil erosion and geotechnical profile installation are provided along with a discussion on the parallel performance of the presented models. The results show that a micromechanical approach can be feasible and useful in practice, providing meaningful insights into complex engineering problems like the erosion kinetics of a soil under an impinging jet or the penetration resistance of a deep foundation in a layered soil profile. KW - Offshore geomechanics KW - Erosion KW - Micromechanical modelling KW - LBM-DEM KW - GPU Parallel computing PY - 2020 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-502309 DO - https://doi.org/10.1016/j.compgeo.2019.103404 VL - 120 SP - Paper 103404, 1 PB - Elsevier Ltd. AN - OPUS4-50230 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Balscheit, Hagen A1 - Geißler, Peter A1 - Cuéllar, Pablo A1 - Basedau, Frank A1 - Baeßler, Matthias T1 - Large-scale field tests on plastic pile tip failure upon monopile installation N2 - Large-diameter monopiles are the most common foundation structures for offshore wind turbines. One relevant failure mode during installation is plastic failure of the pile tip which may increase progressively during further driving (pile tip buckling; extrusion buckling). This paper presents the details and results of a large-scale field-test campaign with dynamic pile installation for the validation and calibration of different numerical approaches concerning pile-tip buckling phenomena. The phenomenology of observed pile-tip failures is here described in detail and a first quantitative approach is evaluated based on the field-test data. As the number of new projects continues to grow and the necessity to construct wind farms in challenging terrain increases, such field data-sets will become increasingly relevant. KW - Monopile KW - Offshore Windenergy KW - Pfahlfußbeulen KW - Pile Tip Buckling KW - Reference Tests PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-611651 DO - https://doi.org/10.1016/j.oceaneng.2024.119322 VL - 313 SP - 1 EP - 14 PB - Elsevier B.V. AN - OPUS4-61165 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Balscheit, Hagen A1 - Victor, A. A1 - Thiele, Marc A1 - Cuéllar, Pablo A1 - Baeßler, Matthias A1 - Lüddecke, F. T1 - Experimental Investigation on Buckling Behavior of soil-embedded Piles N2 - Monopiles are currently the predominant foundation type for offshore wind turbines in Europe. Due to the increasing dimensions of the turbines, pile diameters beyond 10m become necessary. A design-relevant failure mode of monopiles is the local buckling of the pile wall in the embedded sections. Relevant buckling guidelines do not consider the soil-structure interaction specifically, although the embedment may allow for a reduction of wall thickness. However, Eurocode-based design concepts require a validation with comparative buckling cases for validation, either in terms of buckling curve parameters for both the algebraic stress-based and semi-numerical LBA/MNA design concept or as a calibration factor kGMNIA for fully numerical GMNIA calculations. These parameters are not yet available for embedded shells. To close this gap, we have conducted experiments on piles embedded in sand to investigate local buckling under soil-structure-interaction. The results will be used to calibrate numerical models. This research was carried out as part of the VERBATIM research project, funded by PTJ/BMWK and supported by the Carbon Trust's Offshore Wind Accelerator consortium. T2 - EUROSTEEL 2023 CY - Amsterdam, The Netherlands DA - 11.09.2023 KW - Wind KW - Wind Energy KW - Shell Buckling KW - Offshore KW - Soil-Structure-Interaction PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-583641 DO - https://doi.org/10.1002/cepa.2313 SN - 2509-7075 VL - 6 IS - 3-4 SP - 1729 EP - 1734 PB - Ernst & Sohn Gmb AN - OPUS4-58364 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zinas, Orestis A1 - Papaioannou, Iason A1 - Schneider, Ronald A1 - Cuéllar, Pablo A1 - Baeßler, Matthias T1 - 3D spatial modelling of CPT data for probabilistic preliminary assessment of potential pile tip damage upon collision with boulders N2 - Tip damage of monopiles from boulder collisions during installation has emerged as a critical design issue, primarily due to the combination of the widespread use of large-diameter piles and the complexity of the ground conditions at the available sites. Recently, a framework relating potential pile tip damage to cone tip resistance from Cone Penetration Tests (CPTs) has been proposed in the literature. Gaussian processes are powerful stochastic models that enable probabilistic spatial interpolation of soil data at any location within a site. On this basis, this study utilizes sparse CPT data from a site in the North Sea, to first develop an efficient Gaussian process regression model, which is used to derive a three-dimensional (3D) probabilistic predictive map of the cone tip resistance. Assuming deterministic loading conditions and a factual collision with a boulder of pre-defined properties, the cone tip resistance predictive model is subsequently used for a probabilistic preliminary assessment of potential pile tip damage. Results of the analysis are realistic 3D probability maps of potential damage that aim to support engineering judgment and contribute towards cost-effective site investigation planning and offshore wind farm design. T2 - 5th International Symposium on Frontiers in Offshore Geotechnics (ISFOG 2025) CY - Nantes, France DA - 09.06.2025 KW - CPT data KW - Gaussian process regression KW - Boulder impact KW - Preliminary pile tip damage assessment PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-634417 SN - 978-2-85782-758-0 DO - https://doi.org/10.53243/ISFOG2025-323 SP - 505 EP - 510 PB - International Society for Soil Mechanics and Geotechnical Engineering CY - London AN - OPUS4-63441 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CHAP A1 - Baeßler, Matthias A1 - Cuéllar, Pablo A1 - Victor, A. A1 - Lüddecke, F. ED - Triantafyllidis, T. T1 - Stability and large deformations of slender structures supported by soil materials N2 - The stability and geometric nonlinearities of slender structures are a major topic in structural design. While this topic is most relevant in the field of Structural Engineering, e.g. for steel or concrete structures, only few applications take the role of soil-structure-interaction explicitly into account. The focus of this paper is placed on the impact of soil support and its modelling for the buckling analysis based on examples both for pile foundations and for railway track stability. The general interaction between steel design and the geotechnical input will be addressed. The paper discusses and summarizes a range of subtopics based on experience and current research at the author’s institute. KW - Buckling soil-structure-interaction offshore piles track PY - 2020 SN - 978-3-030-28515-9 SN - 978-3-030-28516-6 DO - https://doi.org/10.1007/978-3-030-28516-6 SN - 1613-7736 SN - 1860-0816 VL - 91 SP - 355 EP - 369 PB - Springer CY - Cham, Switzerland AN - OPUS4-49166 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Kemmler, Samuel A1 - Cuéllar, Pablo A1 - Rettinger, C. A1 - Köstler, H. T1 - A Fluid-Solid Coupled Micromechanical Simulation for the Analysis of Piping Erosion During the Seabed Installation of a Suction Bucket Foundation N2 - Suction buckets are a promising concept for the foundations of offshore wind turbines. During the installation process of a suction bucket, localized fluidization of the granular soil, so-called piping erosion, may lead to installation failure. A 3D fluid-solid coupled micromechanical simulation is presented to study the occurrence of piping. An Euler-Lagrangian coupling employs momentum exchange between the fluid phase and the geometrically resolved particles. We investigate the behavior of the soil for three cases with varying prescribed suction velocities. We observe piping in the case with the highest suction velocity by analyzing the deformation of the granular fabric and monitoring the differential pressure. The grains under the bucket wall-tip show the highest hydraulic gradients and forces at the onset of piping. This approach permits a detailed analysis of piping phenomena and brings novel insights on the triggering conditions for piping failure of suction-aided foundations. T2 - TC 105 International Symposium CY - Grenoble, France DA - 23.09.2024 KW - Micromechanical simulation KW - Piping erosion KW - Suction bucket foundation PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-629461 DO - https://doi.org/10.1088/1755-1315/1480/1/012024 SN - 1755-1307 VL - 1480 IS - 1 SP - 1 EP - 4 PB - IOP Publishing AN - OPUS4-62946 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kemmler, Samuel A1 - Cuéllar, Pablo A1 - Artinov, Antoni A1 - Luu, Li-Hua A1 - Farhat, Abbas A1 - Philippe, Pierre A1 - Rettinger, Christoph A1 - Köstler, Harald T1 - A fully-resolved micromechanical simulation of piping erosion during a suction bucket installation N2 - Granular fluidization phenomena such as piping erosion represent a challenge to the delicate installation process of offshore suction bucket foundations. A detailed analysis of the complex conditions in terms of soil composition, soil state, and foundation installation parameters that may lead to piping can be very demanding, if at all possible, solely by experimental means or using macroscopic continuum-based seabed models. The present paper presents a fully-resolved fluid-coupled micromechanical approach for a three-dimensional numerical simulation of the installation process of a suction bucket using the lattice Boltzmann method and discrete element method. The developed model is validated using well-established benchmarks and calibrated by means of experimental data from physical model tests on relevant scenarios focusing on the local fluidization of fixed embedded suction buckets as well as on the suction-driven installation of unrestrained buckets. The qualitative and quantitative agreement with the experimental data both endorse the proposed methodology and highlight the physical soundness of the obtained results. Thereby, the paper shows that three-dimensional analyses of relevant local scenarios at a real scale with little macromechanical model assumptions are feasible. KW - Micromechanical simulation KW - Fluid–solid coupling KW - Piping erosion KW - Suction bucket foundation KW - Offshore wind support structure KW - High-performance computing PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-633790 DO - https://doi.org/10.1016/j.compgeo.2025.107375 SN - 0266-352X VL - 186 SP - 1 EP - 17 PB - Elsevier B.V. AN - OPUS4-63379 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Baeßler, Matthias A1 - Cuéllar, Pablo A1 - Schepers, Winfried T1 - VERBATIM: Project Introduction and Large Scale Experiments N2 - The presentation summarizes the scope of the joint project VERBATIM on buckling of large Monopiles. The presented work from the authors focusses on the experimental field tests of large predented piles during driving and a numerical investigation on the observed buckling behaviour. T2 - Colloquium „Buckling of Offshore Wind Energy Structures“ CY - Berlin, Germany DA - 14.02.2024 KW - Buckling KW - Offshore KW - Wind Energy Structures KW - Monopiles KW - Pile-Tip-Buckling PY - 2024 AN - OPUS4-59535 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zinas, Orestis A1 - Papaioannou, Iason A1 - Schneider, Ronald A1 - Cuéllar, Pablo T1 - Multivariate Gaussian Process for 3D subsurface stratigraphy prediction from CPT and labelled borehole data N2 - Quantifying uncertainties in subsurface properties and stratigraphy can lead to better understanding of the ground conditions and enhance the design and assessment of geotechnical structures. Several studies have utilized Cone Penetration Test (CPT) data and employed Bayesian and Machine Learning methods to quantify the geological uncertainty, based on the Robertson’s soil classification charts and the Soil Behaviour Type Index (Ic). The incorporation of borehole data can reduce the stratigraphic uncertainty. Significant challenges can arise, however, mainly due to the intrinsic differences between field and laboratory-based soil classification systems, which can potentially lead to inconsistent soil classification. To this end, this study proposes a multivariate Gaussian Process model that utilizes site-specific data and: i) jointly models multiple categorical (USCS labels) and continuous (Ic) variables, ii) learns a (shared) spatial correlation structure and the betweenoutputs covariance, and iii) produces two types of dependent classification outputs. The results indicate that the integration of geotechnical and geological information into a unified model can provide more reliable predictions of the subsurface stratification, by allowing simultaneous interpretation of USCS and Ic profiles. Importantly, the model demonstrates the potential to integrate multiple variables of different types, aiming to contribute to the development of a methodology for joint modeling of geotechnical, geological and geophysical data. T2 - 7th International Conference on Geotechnical and Geophysical Site Characterization CY - Barcelona, Spain DA - 18.06.2024 KW - Geotechnical site-characterization KW - Probabilistic KW - Soil classification KW - Gaussian Process PY - 2024 SP - 1733 EP - 1740 AN - OPUS4-60712 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Zinas, Orestis A1 - Papaioannou, Iason A1 - Schneider, Ronald A1 - Cuéllar, Pablo T1 - Spatial modeling of heterogeneous geotechnical site investigation data using multivariate Gaussian Process N2 - This presentation is part of the Engineering Risk Analysis group open seminars. It aims to showcase the results of an ongoing study centered on developing a novel probabilistic methodology for 3D geotechnical site characterization. This methodology integrates data from Cone Penetration Tests (CPTs) and categorical borehole data. The presentation covers the mathematical details of the proposed Multivariate Gaussian Process model and demonstrates its application to a real geotechnical site in New Zealand. T2 - ERA Seminars CY - Munich, Germany DA - 24.07.2024 KW - Geotechnical site-characterization KW - CPT KW - Boreholes KW - Gaussian Process PY - 2024 AN - OPUS4-60716 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Cuéllar, Pablo T1 - Geotechnical challenges in the field of Offshore Wind Energy. Micromechanical perspectives beyond the FEM N2 - This talk provides a brief overview on some geomechanical phenomena and problematic issues in the field of offshore wind-energy geotechnics, with reference to their associated challenges for a numerical analysis/simulation. These may include large deformations, fluid coupling and grain-scale phenomena, all of which are generally difficult to be addressed with conventional FE techniques. These challenges are illustrated here with a practical example for the retrofit of axially loaded piles using compaction grouting techniques. In this case, the mechanical effects of the retrofit may be analysed with standard FE techniques, but require the adoption of strong assumptions, while the injection process itself can only be analysed with special techniques such as the MPM. Finally, an LBM-DEM framework for the micromechanical analysis of such problems is introduced and a practical application for the estimation of the soil resistance to driving (SRD) in layered profiles is discussed. T2 - Online Symposium on Meshfree models for Engineers: Where are they really worthwhile? CY - Online meeting DA - 01.12.2022 KW - Offshore wind energy KW - Offshore geotechnics KW - Micromechanical simulation KW - LBM-DEM KW - Pile retrofit system PY - 2022 AN - OPUS4-56450 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Farhat, Abbas A1 - Philippe, Pierre A1 - Luu, Li-Hua A1 - Doghmane, Alexis A1 - Cuéllar, Pablo T1 - Hydraulic failure of granular materials with artificial cementation N2 - This paper presents an experimental study on the hydraulic failure of a submerged layer of cemented soil stressed by a localized upward water flow. Different mixtures of glass beads bonded with solid paraffin bridges were used as artificial material for the cemented granular soil. Variations in the cementation strength of the material were carefully introduced with different particle sizes and binder contents. The hydraulic fracture tests were then carried out with an upward flow injected at a controlled rate through a small section at the bottom of the samples. From a phenomenological perspective, the results reveal the existence of at least three modes of failure for a cemented soil layer: (1) overall block uplift, (2) block rupture by median crack at the inflow zone, and (3) progressive excavation of a fluidized path along the walls. The critical flow rate and pressure drop conditions at failure have been carefully quantified for the different mixtures and layer thicknesses, leading to a fair estimation of the hydraulic resistance of the samples, which here is found to be virtually independent of the grain size. However, the test results also showed inconsistent failure modes precluding so far the derivation of a simple phase diagram. Nevertheless, it was possible to rationalize all the measured data by employing appropriate modifications of the classical dimensionless numbers that describe the fluidization of purely frictional materials, whereby the cementation strength of the soil is quantified at the microscale through the yield tensile force of the intergranular bonds. Irrespective of its subsequent development, during which boundary conditions obviously play a major role, the initiation of the instability appears to take place very locally at the inlet when the drag force induced by the flow overcomes the cementation strength of the paraffin bonds. The results of this study thus appear to endorse the extension of the dimensional relationships of particulate systems in interaction with fluid flows to the case of cemented granular materials, in a similar vein as in recent previous studies. KW - Fluidized beds KW - Granular materials KW - Fluid Dynamics KW - Cemented soil PY - 2024 DO - https://doi.org/10.1103/PhysRevFluids.9.064305 SN - 2469-990X VL - 9 IS - 6 SP - 1 EP - 13 PB - American Physical Society AN - OPUS4-60803 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Brunier-Coulin, F. A1 - Cuéllar, Pablo A1 - Philippe, P. T1 - Generalized Shields criterion for weakly cohesive granular materials N2 - The erosion of natural sediments by a superficial fluid flow is a generic situation in many usual geological or industrial contexts. However, there is still a lack of fundamental knowledge about erosional processes, especially concerning the role of internal cohesion and adhesive stresses on issues such as the critical flow conditions for the erosion onset or the kinetics of soil mass loss. This contribution investigates the influence of cohesion on the surface erosion by an impinging jet flow based on laboratory tests with artificially bonded granular materials. The model samples are made of spherical glass beads bonded either by solid bridges made of resin or by liquid bridges made of a highly viscous oil. To quantify the intergranular cohesion, the capillary forces of the liquid bridges are here estimated by measuring their main geometrical parameters with image-processing techniques and using well-known analytical expressions. For the solid bonds, the adhesive strength of the materials is estimated by direct measurement of the yield tensile forces and stresses at the particle and sample scales, respectively, with specific traction tests developed for this purpose. The proper erosion tests are then carried out in an optically adapted device that permits a direct visualization of the scouring process at the jet apex by means of the refractive index matching technique. On this basis, the article examines qualitatively the kinetics of the scour crater excavation for both scenarios, namely, for an intergranular cohesion induced by either liquid or solid bonds. From a quantitative perspective, the critical condition for the erosion onset is discussed specifically for the case of the solid bond cohesion. In this respect, we propose here a generalized form of the Shields criterion based on a common definition of a cohesion number from yield tensile values, derived at both micro- and macroscales. The article finally shows that the proposed form manages to reconcile the experimental data for cohesive and cohesionless materials, the latter in the form of the so-called Shields curve along with some previous results of the authors which have been appropriately revisited. KW - Hydraulic jet erosion KW - Cohesive granular materials KW - Jet erosion test PY - 2020 DO - https://doi.org/10.1103/PhysRevFluids.5.034308 VL - 5 IS - 3 SP - 034308 PB - American Physical Society AN - OPUS4-50613 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Cuéllar, Pablo T1 - Deep foundations for offshore wind turbines. Part 2: Lateral behaviour and Advanced topics T1 - Cimentaciones profundas para aerogeneradores marinos. Parte 2: Comportamiento lateral y temas avanzados N2 - his presentation deals with the phenomenology and design of pile foundations for offshore wind turbines, and is divided into two lectures. The second lecture continues with the case of laterally loaded offshore piles, which bears most relevance for the case of the monopile foundations. Here again, a clear separation between physical reality and design methods is intended. Finally, the last part of the second lecture introduces several advanced topics which lie outside the classical design approaches, namely the hydromechanical coupling effects (i.e. the excess pore-pressure generation around the monopiles), the cyclic pile fatigue and the so-called pile setup (i.e. the time effects on the axial pile capacity). The relevance of the latter two topics is illustrated with experimental results from a field testing campaign on real large-scale piles. T2 - CEDEX-UNED 2021 Master course on Soil Mechanics and Geotechnical Engineering CY - Online meeting DA - 24.03.2021 KW - Offshore wind energy KW - Deep foundations KW - Offshore geomechanics KW - Lateral load bearing KW - Cyclic degradation KW - Pile ageing PY - 2021 AN - OPUS4-52342 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Cuéllar, Pablo T1 - Deep foundations for offshore wind turbines. Part 1: Axial behaviour T1 - Cimentaciones profundas para aerogeneradores marinos. Parte 1: Comportamiento axial N2 - This presentation deals with the phenomenology and design of pile foundations for offshore wind turbines, and is divided into two lectures. The first lecture presents a brief introduction to the context and peculiarities of such foundations, and then focuses on the particular case of axially loaded piles. This part is most relevant for the relatively slender piles of the multi-pile substructures (i.e. jackets and tripods). A clear distinction between physical phenomenology and practical design is drawn here. T2 - CEDEX-UNED 2021 Master course on Soil Mechanics and Geotechnical Engineering CY - Online meeting DA - 24.03.2021 KW - Offshore wind energy KW - Deep foundations KW - Offshore geomechanics KW - Axial load bearing KW - Design models PY - 2021 AN - OPUS4-52341 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Cuéllar, Pablo T1 - Deep foundations for offshore wind turbines. Lecture 1: Axial behaviour T1 - Cimentaciones profundas para aerogeneradores marinos - Parte 1: Comportamiento axial N2 - This presentation deals with the phenomenology and design of pile foundations for offshore wind turbines, and is divided into two lectures. The first lecture presents a brief introduction to the context and peculiarities of such foundations, and then focuses on the particular case of axially loaded piles. This part is most relevant for the relatively slender piles of the multi-pile substructures (i.e. jackets and tripods). A clear distinction between physical phenomenology and practical design is drawn here. T2 - Masters course on Soil Mechanics and Geotechnical Engineering. Geotechnical Laboratory of CEDEX CY - Online meeting DA - 21.04.2020 KW - Pile foundations KW - Offshore wind turbines KW - Physical phenomenology KW - Design methods PY - 2020 AN - OPUS4-51057 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Cuéllar, Pablo T1 - Deep foundations for offshore wind turbines. Lecture 2: lateral behaviour and advanced topics T1 - Cimentaciones profundas para aerogeneradores marinos - Parte 2: Comportamiento lateral y tematica avanzada N2 - This presentation deals with the phenomenology and design of pile foundations for offshore wind turbines, and is divided into two lectures. The second lecture continues with the case of lateraly loaded offshore piles, which bears most relevance for the case of the monopile foundations. Here again, a clear separation between physical reality and design methods is intended. Finally, the last part of the second lecture introduces several advanced topics which lie outside the classical design approaches, namely the hydromechanical coupling effects (i.e. the excess pore-pressure generation around the monopiles), the cyclic pile fatigue and the so-called pile setup (i.e. the time effects on the axial pile capacity). The relevance of the latter two topics is illustrated with experimental results from a field testing campaign on real large-scale piles. T2 - Masters course on Soil Mechanics and Geotechnical Engineering. Geotechnical Laboratory of CEDEX CY - Online meeting DA - 21.04.2020 KW - Pile foundations KW - Offshore wind turbines KW - Physical phenomenology KW - Design methods PY - 2020 AN - OPUS4-51059 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -