Dokument-ID Dokumenttyp Autoren/innen Persönliche Herausgeber/innen Haupttitel Abstract Auflage Verlagsort Verlag Herausgeber (Institution) Erscheinungsjahr Titel des übergeordneten Werkes Jahrgang/Band ISBN Veranstaltung Veranstaltungsort Beginndatum der Veranstaltung Enddatum der Veranstaltung Ausgabe/Heft Erste Seite Letzte Seite URN DOI Lizenz Datum der Freischaltung OPUS4-39585 Vortrag Cuéllar, Pablo Deep foundations for offshore wind turbines In this lecture, both the physical behaviour and the general design procedures for deep foundations in the context of the offshore wind energy generation are presented. The first part of the lecture deals with the phenomenology and design of the pile foundations relative to the bearing of axial loads. The second part dwelves on the particularities of the lateral loads as well as on two research topics beyond the current design procedures, namely the hydromechanical coupling and the aging and fatigue phenomena as observed in the course of large-scale field tests. 2017 Internation Masters Course on Soil Mechanics and Geotechnical Engineering Geotechnical Laboratory of CEDEX, Madrid, Spain 27.03.2017 2017-03-29 OPUS4-39426 Zeitschriftenartikel Brunier-Coulin, F.; Cuéllar, Pablo; Philippe, P. Erosion onset of a cohesionless granular medium by an immersed impinging round jet Among different devices developed quite recently to quantify the resistance to erosion of natural soil within the broader context of dyke safety, the most commonly used is probably the jet erosion test in which a scouring crater is induced by impingement of an immersed water jet. A comprehensive experimental investigation on the jet erosion in the specific situation of a cohesionless granular material is presented here. The tests were performed by combining special optical techniques allowing for an accurate measurement of the scouring onset and evolution inside an artificially translucent granular sample. The impinging jet hydrodynamics are also analyzed, empirically validating the use of a self-similar theoretical framework for the laminar round jet. The critical conditions at the onset of erosion appear to be best described by a dimensionless Shields number based on the inertial drag force created by the fluid flow on the eroded particles rather than on the pressure gradients around them. To conclude, a tentative empirical model for the maximal flow velocity initiating erosion at the bottom of the scoured crater is put forward and discussed in the light of some preliminary results. 2017 Physical Review Fluids 2 3 Article 034302, 1 19 10.1103/PhysRevFluids.2.034302 2017-04-11 OPUS4-42459 Vortrag Cuéllar, Pablo Erosive phenomena at the mesoscale - Perspectives and challenges using coupled LBM-DEM models The physical phenomena related to the erosion of granular materials by a fluid flow are ubiquitous and often present major challenges and threats to a wide range of civil engineering constructions and infrastructures. Catastrophic earth-dam failures and large sinkholes are just some of the possible outcomes of the different forms of erosion (a.o. surface erosion, suffusion, piping, backwards erosion, etc…). However, little is known about the actual mechanical origins of erosion, while the assessment of erodibility is generally performed by means of experimental tests and empirical correlations. Here we provide a general overview of some current research models aiming to clarify the micromechanical phenomena and their macromechanical consequences taking place in different erosion scenarios. The employed numerical techniques rely on the coupling of two well-stablished particle methods for the fluid and solid phases, namely the Lattice Boltzmann Method (LBM) and the Discrete Element Method (DEM) respectively. Further ingredients of our numerical models include an elastoplastic cohesion model for intergranular solid bridges and a subcritical debonding model for the simulation of transient damage processes within the soil matrix. 2017 5th Int. Conference on Particle-based Methods (PARTICLES 2017) Hannover, Germany 26.09.2017 28.09.2017 2017-10-11 OPUS4-41121 Beitrag zu einem Tagungsband Brunier-Coulin, F.; Sarrat, J.-L.; Cuéllar, Pablo; Philippe, P. Experimental investigation of impinging jet erosion on model cohesive granular materials Erosion of soils affects both natural landscapes and engineering constructions as embankment dams or levees. Improving the safety of such earthen structures requires in particular finding out more about the elementary mechanisms involved in soil erosion. Towards this end, an experimental work was undertaken in three steps. First, several model materials were developed, made of grains (mostly glass beads) with solid bridges at particle contacts whose mechanical yield strength can be continuously varied. Furthermore, for most of them, we succeeded in obtaining a translucent system for the purpose of direct visualization. Second, these materials were tested against surface erosion by an impinging jet to determine a critical shear stress and a kinetic coefficient. Note that an adapted device based on optical techniques (combination of Refractive Index Matching and Planar Laser Induced Fluorescence) was used specifically for the transparent media. Third, some specifically developed mechanical tests, and particularly traction tests, were implemented to estimate the mechanical strength of the solid bridges both at micro-scale (single contact) and at macro-scale (sample) and to investigate a supposed relationship with soil resistance to erosion. The European Physical Journal (EPJ) - Web of Conferences 2017 Powders and Grains 2017 – 8th International Conference on Micromechanics on Granular Media 140 8th International Conference on Micromechanics on Granular Media Montpellier, France 03.07.2017 07.07.2017 Paper 08002, 1 Paper 08002, 4 urn:nbn:de:kobv:b43-411215 10.1051/epjconf/201714008002 http://creativecommons.org/licenses/by/3.0/de/deed.de 2017-07-26 OPUS4-41122 Posterpräsentation Cuéllar, Pablo Micromechanics of jet erosion on cohesive soils - A coupled LBM-DEM modelling approach Here we investigate the physical mechanisms behind the surface erosion of a cohesive granular soil induced by an impinging jet by means of numerical simulations coupling fluid and grains at the microscale. The 2D numerical model combines the Discrete Element and Lattice Boltzmann methods (DEM-LBM) and accounts for the granular cohesion with a contact model featuring a paraboloidal yield surface. Here we review first the hydrodynamical conditions imposed by the fluid jet on a solid granular packing, turning then the attention to the impact of cohesion on the erosion kinetics. Finally, the use of an additional subcritical debonding damage model based on the work of Silvani and co-workers provides a novel insight into the internal solicitation of the cohesive granular sample by the impinging jet. 2017 8th International Conference on Micromechanics on Granular Media Montpellier, France 03.07.2017 07.07.2017 2017-07-26 OPUS4-41118 Beitrag zu einem Tagungsband Cuéllar, Pablo; Benseghier, Z.; Luu, L.-H.; Bonelli, S.; Delenne, J.-Y.; Radjai, F.; Philippe, P. Numerical insight into the micromechanics of jet erosion of a cohesive granular material Here we investigate the physical mechanisms behind the surface erosion of a cohesive granular soil induced by an impinging jet by means of numerical simulations coupling fluid and grains at the microscale. The 2D numerical model combines the Discrete Element and Lattice Boltzmann methods (DEM-LBM) and accounts for the granular cohesion with a contact model featuring a paraboloidal yield surface. Here we review first the hydrodynamical conditions imposed by the fluid jet on a solid granular packing, turning then the attention to the impact of cohesion on the erosion kinetics. Finally, the use of an additional subcritical debonding damage model based on the work of Silvani and co-workers provides a novel insight into the internal solicitation of the cohesive granular sample by the impinging jet. The European Physical Journal (EPJ) - Web of Conferences 2017 Powders and Grains 2017 – 8th International Conference on Micromechanics on Granular Media 140 8th International Conference on Micromechanics on Granular Media Montpellier, France 03.07.2017 07.07.2017 Paper 15017, 1 Paper 15017, 4 urn:nbn:de:kobv:b43-411186 10.1051/epjconf/201714015017 http://creativecommons.org/licenses/by/3.0/de/deed.de 2017-07-26 OPUS4-42962 Beitrag zu einem Tagungsband Kullolli, Borana; Cuéllar, Pablo; Baeßler, Matthias On contact problem application for the local behavior of soil-pile interaction In this paper a shear test, which helps to study local behavior of the soil-pile interaction, is modelled numerically with the Finite Element Method as a 2D plane strain problem. A normal pressure on top and shear displacement on side were applied. So far, the material behavior was considered elastic for the sake of simplicity. The effect of thickness on contact elements and the presence of in plane stress has been highlighted. The purpose of the paper is to find a suitable contact element which represents more close to reality a soil-pile interaction problem under cyclic axial loading. Moreover, an insight on the presence of in-plane stress shows that it needs to be considered cautiously. Tirana, Albania Polytechnic University of Tirana Polytechnic University of Tirana 2017 Book of Proceedings ICCE2017 ICCE2017 Tirana, Albania 12.10.2017 14.10.2017 167 174 2017-11-20 OPUS4-41119 Beitrag zu einem Tagungsband Philippe, P.; Cuéllar, Pablo; Brunier-Coulin, F.; Luu, L.-H.; Benahmed, N.; Bonelli, S.; Delenne, J.-Y. Physics of soil erosion at the microscale We focus here on the major and still relevant issue of soil erosion by fluid flows, and more specifically on the determination of both a critical threshold for erosion occurrence and a kinetics that specifies the rate of eroded matter entrainment. A state-of-the-art is first proposed with a critical view on the most commonly used methods and erosion models. It is then discussed an alternative strategy, promoting the use of model materials that allow systematic parametric investigations with the purpose of identifying more precisely the local mechanisms responsible for soil particle erosion and ultimately quantifying both critical onsets and kinetics, possibly through existing or novel empirical erosion laws. Finally, we present and discuss several examples following this methodology, implemented either by means of experiments or numerical simulations, and coupling erosion tests in several particular hydrodynamical configurations with wisely selected mechanical tests. The European Physical Journal (EPJ) - Web of Conferences 2017 Powders and Grains 2017 – 8th International Conference on Micromechanics on Granular Media 140 8th International Conference on Micromechanics on Granular Media Montpellier, France 03.07.2017 07.07.2017 Paper 08014, 1 Paper 08014, 4 urn:nbn:de:kobv:b43-411198 10.1051/epjconf/201714008014 http://creativecommons.org/licenses/by/3.0/de/deed.de 2017-07-26 OPUS4-39340 Buchkapitel Rücker, Werner; Cuéllar, Pablo; Georgi, Steven; Karabeliov, Krassimire; Baeßler, Matthias; Johnsen, Björn Durstewitz, M.; Lange, B. Please Avoid Tilting - Application-Oriented Design and Monitoring Model for Foundation Structures Subjected to Cyclic Loads A great deal is possible, even on the seabed. Together, wind and waves shake the foundations of the offshore wind turbines. "ere is also the "normal" current and ebb and #ow of the tides that are so distinctive in the North Sea. Pore water pressure can also occur on the seabed, loosening it. Where monopiles are involved, the worst case is that the stability of the whole turbine can be altered - even if such a monopile rammed into the seabed has a diameter of up to eight metres. Over half the planned offshore wind turbines in the North and Baltic Seas are to have monopile foundations, and over 40 % are to have multi-pile foundations, designed for example as a tripod. "is is why pile foundations and their loads deserve special attention. For one thing above all is to be avoided in plant operations, and that is the risk of turbine tilt. Springer 2017 Sea, Wind, Power 978-3-662-53178-5 53 59 10.1007/978-3-662-53179-2 2017-03-14 OPUS4-39341 Buchkapitel Baeßler, Matthias; Cuéllar, Pablo; Georgi, Steven; Karabeliov, Krassimire; Rücker, Werner; Johnsen, Björn Durstewitz, M.; Lange, B. Uncharted Territory on the Seabed - Monitoring Procedures and Assessment Model for the Foundations of Offshore Wind Turbines Offshore wind turbines enter unknown territory, especially where the foundations are concerned. This is because offshore wind power can only make use of the experience from the common offshore constructions used by the oil and gas industry to a limited extent. The offshore wind industry has tried to reduce foundation dimensions, especially the pile lengths, as much as possible compared with those of the oil and gas industry. This is because with the large number of wind turbines involved it can provide considerable economic advantages. On the other hand, the stability of the foundations is additionally at risk because due to the much larger number of cyclic loads they are subjected to it is very difficult to predict how they will behave. Since offshore wind farms are manufactured in series, every systematic fault in the foundation acts as a series fault for a large number of turbines. This calls for monitoring - and the right dimensions of pile foundation, the most common type of foundations used for wind turbines Springer 2017 Sea, Wind, Power 978-3-662-53178-5 61 67 10.1007/978-3-662-53179-2 2017-03-14