14 results on '"Bourrier, Franck"'
Search Results
2. Micromechanical analysis of second order work in granular media
- Author
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Hadda, Nejib, Nicot, François, Bourrier, Franck, Sibille, Luc, Radjai, Farhang, and Darve, Félix
- Published
- 2013
- Full Text
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3. Failure mechanisms in granular media: a discrete element analysis
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Nicot, François, Hadda, Nejib, Bourrier, Franck, Sibille, Luc, and Darve, Félix
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- 2011
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4. Physical processes within a 2D granular layer during an impact
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Bourrier, Franck, Nicot, François, and Darve, Félix
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- 2008
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5. Effet d'échelles: Modélisation numérique des barrages flexibles dans les torrents
- Author
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Li, Shuo, Piton, Guillaume, Bourrier, Franck, Erosion torrentielle neige et avalanches (UR ETGR (ETNA)), and Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA)
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Similarity analysis ,Net barrier ,[SDE.IE]Environmental Sciences/Environmental Engineering ,[SPI.GCIV.RISQ]Engineering Sciences [physics]/Civil Engineering/Risques ,Numerical simulation ,Discrete Element Method ,Debris flow ,[SPI.GCIV.CH]Engineering Sciences [physics]/Civil Engineering/Construction hydraulique - Abstract
Some geohazards such as landslides and debris flow, which have already caused millions of dollars in damage and thousands of deaths and injuries each year, are regarded as a serious threat to humans and infrastructures. Therefore, studies on the design of structural mitigation measures and the related numerical simulation on barriers deformation against debris flow is of crucial importance in terms of engineering application. Motivated to clarify the mechanisms underlying rope nets deformation behavior and further establish a theoretical model for determining an appropriate material under experimental conditions, a series of numerical simulations using an extensive open-source framework called Yade DEM along with its discrete element method (DEM) is being performed by generating a rope net within certain physical properties under different loading conditions on the net nodes. To further understand this behavior, in this paper the scale effect and buckling effect are investigated by Bunkingham-pi theorem and plastic structure respectively. It is found that, a consistent impact of simple load on the net central deformation characteristics (e.g. absolute and relative displacement) under different scales are observed. And the efficiency of basic model including five dimensionless parameters to investigate the scale effect by similarity analysis is confirmable. And the net deformation of a chosen material (PSU) under a small scale (1:30) is in accordance with that of the theoretical material which is defined by basic model. In addition, it seems that, to improve the performance of net barrier against debris flow, the plastic flat region as shown in strain-stress curve should be larger than a certain value. Knowledge and evidence from this work might be utilized for the development and verifications of theoretical model and barriers structure design in the future.
- Published
- 2018
6. Dynamic analysis of wooden rockfall protection structures subjected to impact loading using a discrete element model.
- Author
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Olmedo, Ignacio, Bourrier, Franck, Bertrand, David, Berger, Frédéric, and Limam, Ali
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IMPACT (Mechanics) , *IMPACT loads , *DISCRETE element method , *IMPACT craters , *IMPACT testing - Abstract
Wooden structures made of felled trees are used in forested slopes as protection structures against rockfall. A model based on the Discrete Element Method is developed to analyse their response to normal impacts of blocks. The interaction between the blocks and the stems and the stem response are explicitly integrated. After the model calibration using impact tests, a wide range of impact scenarii representative of real configurations is explored. The influence of three parameters (stem diameter, impact velocity and block diameter) is analysed. Three impact types were identified for different ratios R D between the block and stem diameters. For small R D , the impact is limited to a brief contact. For intermediate R D , successive contacts of similar duration are observed. After the last contact, the block is sent back with a large velocity. For large R D , two contacts are observed. The second contact can be assimilated to a quasi-static loading of the stem. In addition, structure damage increases for increasing R D ranging from almost no damage for the first impact type to rupture of the stem for the third type. The largest R D associated with the first impact type is the target configuration that favours block energy decrease and limits structure damage. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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7. Using the Discrete Element Method for rockfall protection forests efficiency assessment
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Toe, David, Bourrier, Franck, Olmedo-Manich, Ignacio, Bertrand, David, Berger, Frédéric, and Association Française de Mécanique
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forest ,rockfall ,[PHYS.MECA]Physics [physics]/Mechanics [physics] ,Discrete Element Method - Abstract
Colloque avec actes et comité de lecture. Internationale.; International audience; L'évaluation de l'efficacité de la forêt pour la protection contre les chutes de blocs n'est possible que suite à l'étude détaillée de l'impact d'un bloc sur un arbre. Dans cette optique, un modèle basé sur la Méthode des Eléments Discrets a été développé et utilisé pour identifier les paramètres principaux contrôlant la cinématique du bloc après impact sur l'arbre. L'objectif final de ce travail est de construire un méta-modèle de l'interaction entre un bloc et un arbre utilisable en pratique dans les modèles de simulation de la propagation des blocs.
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- 2015
8. A Novel DEM Approach to Simulate Block Propagation on Forested Slopes.
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Toe, David, Bourrier, Franck, Dorren, Luuk, and Berger, Frédéric
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DISCRETE element method , *ROCKFALL , *COPPICE forests , *DEFORMATIONS (Mechanics) , *SIMULATION methods & models - Abstract
In order to model rockfall on forested slopes, we developed a trajectory rockfall model based on the discrete element method (DEM). This model is able to take the complex mechanical processes at work during an impact into account (large deformations, complex contact conditions) and can explicitly simulate block/soil, block/tree contacts as well as contacts between neighbouring trees. In this paper, we describe the DEM model developed and we use it to assess the protective effect of different types of forest. In addition, we compared it with a more classical rockfall simulation model. The results highlight that forests can significantly reduce rockfall hazard and that the spatial structure of coppice forests has to be taken into account in rockfall simulations in order to avoid overestimating the protective role of these forest structures against rockfall hazard. In addition, the protective role of the forests is mainly influenced by the basal area. Finally, the advantages and limitations of the DEM model were compared with classical rockfall modelling approaches. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
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9. Analysis of the effect of trees on block propagation using a DEM model: implications for rockfall modelling.
- Author
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Toe, David, Bourrier, Franck, Olmedo, Ignacio, Monnet, Jean-Matthieu, and Berger, Frédéric
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ROCKFALL , *DISCRETE element method , *KINEMATICS , *KINETIC energy , *PLANT species - Abstract
The objective of this research was to use numerical models based on mechanical approaches to improve the integration of the protective role of forests against rockfall into block propagation models. A model based on the discrete element method (DEM) was developed to take into account the complex mechanical processes involved during the impact of a block on a tree. This modelling approach requires the definition of many input parameters and cannot be directly integrated into block propagation models. A global sensitivity analysis identified the leading parameters of the block kinematics after impact (i.e. block energy reduction, trajectory changes, and rotational velocity): the impact velocity, the tree diameter, and the impact point horizontal location (i.e. eccentricity). Comparisons with the previous experimental and numerical studies of block impacts on trees demonstrated the applicability of the DEM model and showed some of the limitations of earlier approaches. Our sensitivity analysis highlights the significant influence of the impact velocity on the reduction of the block's kinetic energy. Previous approaches usually also focus on parameters such as impact height, impact vertical incidence, and tree species, whose importance is only minor according to the present results. This suggests that the integration of forest effects into block propagation models could be both improved and simplified. The DEM model can also be used as an alternative to classical approaches for the integration of forest effects by directly coupling it with block propagation models. This direct coupling only requires the additional definition of the location and the diameter of each tree. Indeed, the input parameters related to the mechanical properties of the stem and the block/stem interaction in the DEM model can be set to average values because they are not leading parameters. The other input parameters are already defined or calculated in the block propagation model. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
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10. Comparing numerical and experimental approaches for the stochastic modeling of the bouncing of a boulder on a coarse soil
- Author
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Bourrier, Franck, Nicot, François, Eckert, Nicolas, Darve, F., Érosion torrentielle, neige et avalanches (UR ETGR (ETNA)), Centre national du machinisme agricole, du génie rural, des eaux et forêts (CEMAGREF), Ecosystèmes montagnards (UR EMGR), and Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )
- Subjects
rockfall hazard ,[SDE]Environmental Sciences ,impact ,stochastic ,trajectory analysis ,discrete element method ,GeneralLiterature_MISCELLANEOUS - Abstract
International audience; This paper proposes numerical investigations for the stochastic modeling of a boulder impacting a coarse granular soil. The soil is considered as a noncohesive granular medium using a discrete element method and the soil model is calibrated compared to results from half-scale experiments. Based on this numerical model, an extensive numerical simulation campaign is carried out. The statistical analysis of the numerical results allows the definition of a stochastic bouncing model that quantifies most of the variability of the numerical results. Comparisons with classical bouncing models in the field of trajectory analysis highlight that this model expands classical approaches. The comparison of results from real-scale experiments to trajectory simulations based on the stochastic model show the relevance of the proposed approach to modeling rockfall trajectories.
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- 2010
11. Modeling the impact of a boulder on a natural soil, application to rockfall trajectory simulations
- Author
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Bourrier, Franck, Erosion torrentielle neige et avalanches (UR ETGR (ETNA)), Institut national de recherche en sciences et technologies pour l'environnement et l'agriculture (IRSTEA), Laboratoire sols, solides, structures - risques [Grenoble] (3SR), Université Joseph Fourier - Grenoble 1 (UJF)-Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP)-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes (UGA), Institut National Polytechnique de Grenoble - INPG, François Nicot, Félix Darve(francois.nicot@cemagref.fr, felix.darve@inpg.fr), Institut polytechnique de Grenoble - Grenoble Institute of Technology (Grenoble INP )-Université Joseph Fourier - Grenoble 1 (UJF)-Institut National Polytechnique de Grenoble (INPG)-Centre National de la Recherche Scientifique (CNRS), Érosion torrentielle, neige et avalanches (UR ETGR (ETNA)), and Centre national du machinisme agricole, du génie rural, des eaux et forêts (CEMAGREF)
- Subjects
Rockfall ,Granular materials ,Trajectographie ,Trajectory analysis ,Matériaux granulaires ,Stochastic analysis ,Méthode des Eléments Discrets ,Inférence Bayésienne ,Chute de blocs ,[SPI]Engineering Sciences [physics] ,Impact ,Discrete Element Method ,Bayesian inference ,Analyse stochastique - Abstract
This thesis is dedicated to the study of falling rocks bouncing on natural soils in order to improve the models used for rockfall hazard assessment. The impact of a rock on a scree slope is modelled using the Discrete Element Method. The comparison between numerical results and half-scale experimental results of impacts on a coarse soil shows that the numerical model allows accurately predicting the bouncing of the rock for a reduced number of model parameters to be calibrated. The numerical results also emphasize that the interaction between the impacting particle and the granular soil is composed of three stages : the partial energy exchange from the impacting particle to the soil, the propagation of a shockwave from the impact point and the wave reflection on the substratum. The study of energy exchanges during these three stages allows defining the impacting particle bouncing occurrence diagram as well as three impact regimes. The statistical analysis of numerical results using Bayesian inference leads to the definition of a stochastic impact model. This model is relevant for rock velocity after impact depending on both rock velocity before impact and soil particles layout near the impact point. Finally, the stochastic impact model is integrated into trajectory analysis models which allows defining a global probabilistic approach of rockfall hazard assessment including protective structures design.; Ce travail de thèse porte sur la caractérisation du rebond d'un bloc sur un terrain naturel dans la perspective d'améliorer les modèles de détermination de l'aléa de chute de blocs. L'impact d'un bloc rocheux sur un sol composé d'éboulis est modélisé par la Méthode des Elements Discrets. La comparaison entre les résultats de simulation et les résultats d'essais à échelle réduite d'impact sur un sol granulaire grossier met en évidence que le modèle numérique développé assure une prédiction pertinente du rebond pour un nombre réduit de paramètres de simulation à calibrer. L'analyse de l'impact à l'aide du modèle numérique montre que l'interaction entre l'impactant et le sol peut être décomposée en trois phases : le transfert énergétique initial du bloc vers le sol, la propagation d'une onde de compression du point d'impact vers l'intérieur du sol et la réflexion de l'onde de compression sur le substratum. L'étude des échanges énergétiques lors de ces trois phases conduit à la définition d'un diagramme d'existence du rebond délimitant les domaines d'arrêt et de rebond de l'impactant et à l'identification de trois régimes d'impact. Le traitement statistique des résultats de simulation par des méthodes statistiques basées sur l'inférence Bayésienne permet également de définir une loi d'impact stochastique. Cette loi est représentative de la variabilité des vitesses du bloc après impact en fonction des paramètres cinématiques incidents et de l'arrangement géométrique des particules du sol au voisinage du point d'impact. Enfin, suite à l'intégration de la loi stochastique d'impact dans le contexte de l'analyse trajectographique, une approche probabiliste globale permettant la caractérisation détaillée de l'aléa de chute de bloc ainsi que l'implantation et le dimensionnement d'ouvrages de protection est proposée.
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- 2008
12. Discrete modeling of granular soils reinforcement by plant roots.
- Author
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Bourrier, Franck, Kneib, François, Chareyre, Bruno, and Fourcaud, Thierry
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DISCRETE element method , *SOIL granularity , *PLANT roots , *NUMERICAL analysis , *SOIL ecology , *SIMULATION methods & models - Abstract
Abstract: The analysis of the influence of the roots on the shear resistance of the soil requires identifying the effect of the different root–soil interaction processes depending on soil and roots properties. For that purpose, a numerical model of direct shear tests of non-rooted and rooted granular soils based on the Discrete Element Method was developed. The soil is modeled as an assembly of locally interacting spheres and the roots are modeled as deformable cylinders in the soil matrix. The model allows accounting for the root tensile loading until breakage, the root bending loading, the root–soil adhesive links until adhesion breakage, the root slippage associated with a frictional resistance at the root–soil interface. The study focuses on identifying the different root–soil interaction mechanisms depending on the soil type. Both frictional and cohesive granular soil types were used in the simulations. The effects of the roots mechanical properties – tensile, bending modulus and root–soil interfacial friction angle – and of the root number were also analyzed for the different soil types. The results first show that the effect of the roots strongly depends on the shear strain for any soil type. For frictional soils, an increasing shear strain induces progressively a pure tensile loading of the roots until slippage of the root–soil interface. For cohesive granular soils, the pure tensile loading of the roots is followed by a progressive breakage of the adhesive root–soil links and by a complete slippage of the roots. The results show that the influence of the root number is significant if the prevailing processes are root tensile loading combined with slippage whereas it is less important if root loading is combined with progressive breakage of the adhesive links for the root configurations explored. Finally, the results show that the shear strain range associated with the different processes strongly depends on the relative rigidities of the roots and soil matrix. The model developed was shown of great interest to analyze the shear resistance of the rooted soil assemblies depending on the shear strain. Such an approach could therefore be used to test the different assumptions done in the analytical models. Developing analytical models of slope stability based on the calculation of the shear resistance of rooted soil depending not only on soil and root properties but also on shear strain intensity also constitutes a perspective for the use of the model developed. [Copyright &y& Elsevier]
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- 2013
- Full Text
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13. Evolution of the micromechanical properties of impacted granular materials
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Bourrier, Franck, Nicot, François, and Darve, Felix
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MICROMECHANICS , *MECHANICAL behavior of materials , *GRANULAR materials , *FRICTION , *MATHEMATICAL models , *NUMERICAL analysis - Abstract
Abstract: The impact of a projectile on a granular material induces important changes in the micromechanical properties of the impacted material. These changes are studied using a Discrete Element Method model of the impact. The numerical results show that the impact first entails an energy propagation from the impact point to the limit of the sample through the existing force chains. A significant kinetic energy and a total breakage of the existing contact force chains are the main consequences of the energy propagation. During the long recovery balance phase observed after the energy propagation phase, frictional processes cause the kinetic energy dissipation. The motions of the particles and the numerous contact openings first prevent the formation of stable force chains. However, for long durations after the beginning of the impact, contact openings stop. The balance recovery phase therefore finally results in the creation of new stable contact force networks. [Copyright &y& Elsevier]
- Published
- 2010
- Full Text
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14. Assessment of the predictive capabilities of discrete element models for flexible rockfall barriers.
- Author
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Dugelas, Loïc, Coulibaly, Jibril B., Bourrier, Franck, Lambert, Stéphane, Chanut, Marie-Aurélie, Olmedo, Ignacio, and Nicot, François
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DISCRETE element method , *TWO-dimensional bar codes , *TENSILE tests , *IMPACT (Mechanics) - Abstract
• Two different DEM models used to predict the barrier response under various loadings • Analysis of the experimental barrier response under single and successive impacts • The discrete element method is assessed for flexible rockfall barrier modeling This paper addresses the use of discrete element modeling approaches for predicting the impact response of flexible rockfall protection barriers. In this purpose, two different models are considered and their results are compared to detailed results from full-scale impact experiments. The studied barrier is a prototype made from a 4-contacts ring net and having a 270 kJ nominal capacity. The two discrete elements method models, developed by separate entities with different codes (Yade-DEM and GENEROCK), use different models for the ring net, the cables and cable-net connections, while other structural elements are modelled the same way : posts, anchors, energy dissipating devices, and boulder. The models for the structural elements (ring net, energy dissipating devices) are calibrated individually from quasi-static tensile tests results. The barrier model is then created assembling the structural elements, before being impacted. The tests consist in a impacting in its center a 3-module barrier, first, to one high kinetic energy impact and, second, to three consecutive impacts with a lower kinetic energy. The models results are confronted to measurements made during the experiments, considering a large set of parameters. Both models reveal satisfactory in predicting the structure response, on quantitative and qualitative points of view, and considering the boulder displacement, forces in the main cables and forces acting within the various energy dissipating devices. The quality of the prediction by each model compared to the other depends on the considered parameter. Little deviations from the experimental results are attributed to the model calibration procedure and to slight differences between the real structure and the modeled ones. In the end, the DEM approach appears suitable for modelling flexible barriers in complex loading conditions (high velocity and successive impacts). [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
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