TY - CONF A1 - Sanayei, Mohammad Hassan A1 - Farhat, A. A1 - Luu, Li-Hua A1 - Werner, L. A1 - Rettinger, C. A1 - Philippe, P. A1 - Cuéllar, Pablo T1 - Micromechanical framework for a 3D solid cohesion model - Implemantation, validation and perspectives N2 - This article presents a solid cohesion model for the simulation of bonded granular assemblies in the frame of 3D discrete element approaches (DEM). A simple viscoplastic cohesion model for 2D geometries is extended to 3D conditions, while its yield criterion is generalized as a hyper-surface in the space of bond solicitations to include torsional moments. The model is then calibrated using experimental results of uniaxial traction at both the microscopic and macroscopic scales with an artificial granular cohesive soil. The paper finally presents some simulated results on the macromechanical sample traction application and briefly discusses the model's current limitations and promising prospects for subsequent works. T2 - VII International Conference on Particle-Based Methods PARTICLES 2021 CY - Hamburg, Germany DA - 04.10.2021 KW - Granular Cohesive Materials, KW - DEM KW - Micromechanical Tensile Failure KW - Macromechanical Sample Strength PY - 2021 AN - OPUS4-53726 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 - 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 - 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 -