Félix Darve - Academia.edu (original) (raw)

Papers by Félix Darve

Proceedings 3rd International Conference on Scour and Erosion (ICSE-3). November 1-3, 2006, Amsterdam, The Netherlands, Nov 1, 2006

In this paper, the influence of strain and stress loading paths on the behavior of very loose san... more In this paper, the influence of strain and stress loading paths on the behavior of very loose sand is analyzed with particular attention to potential instabilities. A particular stress path, i.e. a quasi constant shear undrained path, is presented and comparisons are made with data from literature. Experimental results show that diffuse mode failure occurs before the Mohr-Coulomb failure surface is reached. It is shown for these undrained tests that excess pore pressure results from collapse and it is not a trigger parameter. Moreover, stress ratios at collapse and corresponding mobilized angle of friction are very close for classical consolidated undrained tests, constant shear drained tests and quasi constant shear undrained tests. The onset of collapse is thus independent of the loading path under drained and undrained conditions but depend on the direction of the stress increment.

DANS UNE PREMIERE PARTIE, LES AUTEURS UTILISENT UN MODELE RHEOLOGIQUE INCREMENTAL INTERGRANUALIRE... more DANS UNE PREMIERE PARTIE, LES AUTEURS UTILISENT UN MODELE RHEOLOGIQUE INCREMENTAL INTERGRANUALIRE POUR PREVOIR LE COMPORTEMENT HOMOGENE NON DRAINE D'UN ECHANTILLON SATURE D'ARGILE OU DE SABLE. CETTE ANALYSE EST REALISEE EN CONTRAINTES EFFECTIVES ET CONDUIT A LA PREVISION DE LA PRESSION INTERSTITIELLE EN IMPOSANT LA NON-VARIATION DE VOLUME. LES RESULTATS SONT CONFRONTES A L'EXPERIENCE. DANS LA SECONDE PARTIE, LES AUTEURS PROPOSENT ET APPLIQUENT UNE METHODE DE CALCUL DES PRESSIONS INTERSTITIELLES DANS LES OUVRAGES NON DRAINES, METHODE UTILISANT EGALEMENT DES CARACTERISTIQUES MECANIQUES INTERGRANULAIRES ET UNE ANALYSE EN CONTRAINTES EFFECTIVES. LES APPLICATIONS PORTENT SUR LA PREVISION DES PRESSIONS INTERSTITIELLES AU VOISINAGE D'UN PIEU SOLLICITE A L'ARRACHEMENT, LE SOL ETANT SUPPOSE ELASTIQUE, AINSI QUE SUR LE CALCUL DU CHAMP DE PRESSION INTERSTITIELLE ET DES CHEMINS EN CONTRAINTES EFFECTIVES, DANS UN ESSAI TRIAXIAL LOCALEMENT OU GLOBALEMENT NON DRAINE. (A).

Computers and Geotechnics, 2021

The proper solution of geotechnical boundary value problems requires robust constitutive models t... more The proper solution of geotechnical boundary value problems requires robust constitutive models that can describe the mechanical behavior of geomaterials under various loading conditions, while also accounting as closely as possible for the different material scales of interest. This is even more relevant to granular media where the complexity of the mechanical behaviour is not limited to the nature of the contact law between grains, and instead originates from the multiplicity of contacts oriented along all the directions of the physical space to form distinctive mesostructures. This paper revisits the so-called H-model, which belongs to the broad family of micromechanical approaches whereby an intermediate scale (mesoscale) is explicitly introduced into the formulation. One great advantage of the model is that it can be extended by accounting for further multi-physical couplings, as for example the presence of capillary bridges between grains. This versatile model was implemented within an explicit finite difference based computational software (FLAC), and the present work demonstrates its ability to analyze engineering problems with a microstructural viewpoint, while also providing new insights in microstructural mechanisms of failure difficult to capture with standard phenomenological models.

Geometric Science of Information, 2017

Symplectic structure is powerful especially when it is applied to Hamiltonian systems. We show he... more Symplectic structure is powerful especially when it is applied to Hamiltonian systems. We show here how this symplectic structure may define and evaluate an integer index that measures the defect for the system to be Hamiltonian. This defect is called the Geometric Degree of Non Conservativeness of the system. Darboux theorem on differential forms is the key result. Linear and non linear frameworks are investigated.

Revue Française de Géotechnique, 1983

Natural Hazards and Earth System Sciences Discussions, 2019

A translational landslide comprising nearly horizontal sand and mud interbed was widely developed... more A translational landslide comprising nearly horizontal sand and mud interbed was widely developed in the Ba river basin of the Qinba-Longnan mountain area. Scholars have conducted theoretical research on this rainfall-induced landslide; however, owing to the lack of landslide monitoring engineering and data, demonstrating and validating the theoretical research wasdifficult. This study considered a translational landslide with an unusual morphology: the Wobaoshi landslide, which is located in Bazhong city, China. First, the formation conditions of this landslide were ascertained through field exploration, and the deformation and failure characteristics of the plate-shaped sliding body were analyzed. Then, long-period monitoring engineering was conducted to obtain multi-parameter monitoring data, such as crack width, rainfall intensity, and pore-water pressure. Finally, through the mechanical model analysis of the multi-stage sliding bodies, the calculating formula of the maximum height of the multi-stage plate girders, hcr, was derived， and the long-period monitoring data were used to verify its accuracy. Combined with numerical simulation and calculations, the deformation and failure modes of the plate-shaped sliding bodies were analyzed and explored. In this paper, the multi-parameter monitoring data proved that the stability of the sliding body is affected greatly by the rainfall

Natural Hazards and Earth System Sciences Discussions, 2018

Rockslides are a common and devastating problem affecting mining and other engineering activities... more Rockslides are a common and devastating problem affecting mining and other engineering activities all over the world; consequently, there have been many studies into their prediction and prevention. This study focused on a recent rockslide in an open pit mine in Liaoning province, China. The stability of the rock slope under excavation and rainfall conditions was monitored using an efficient real-time monitoring system. A further numerical analysis was performed using the Finite Element Method with Lagrangian Integration Points (FEMLIP), and the normalized global second order work was implanted to assess the structure instability as a safety factor. In fact for the future it would be very interesting to compare in real time measurements and simulations, and not only to develop back computations after failure. The numerical results indicate that the rock slope remained stable during excavation, yet lost stability after subsequent rainfall. Water infiltration, along with a major geological discontinuity, degraded the strength of the weak zone and induced the rockslide. The monitoring approach presented its robustness and generality, and was worth being generalized. The numerical approach proposed the evolution of the safety factor, comparing the monitoring data, and the mechanism of the rockslide was determined. It could be used as an assistant tool for the disaster predictions.

ZAMM - Journal of Applied Mathematics and Mechanics / Zeitschrift für Angewandte Mathematik und Mechanik, 2017

In this paper we deal with recent results on divergence kinematic structural stability (ki.s.s.) ... more In this paper we deal with recent results on divergence kinematic structural stability (ki.s.s.) resulting from discrete nonconservative finite systems. We apply them to continuous nonconservative systems which are shown in the well-known Beck column. When the column is constrained by an appropriate additional kinematic constraint, a certain value of the follower force may destabilize the system by divergence. We calculate its minimal value, as well as the optimal constraint. The analysis is carried out in the general framework of inÞnite dimensional Hilbert spaces and non-self-adjoint operators.

Applied Mathematical Modelling, 2016

This paper deals with nonconservative mechanical systems as those subjected to nonconservative po... more This paper deals with nonconservative mechanical systems as those subjected to nonconservative positional forces and leading to non-symmetric tangential stiffness matrices. In a previous work, the geometric degree of nonconservativity of such systems, defined as the minimal number of kinematic constraints necessary to convert the initial system into a conservative one is found to be, in the linear framework, the half of the rank of the skewsymmetric part of the stiffness matrix. In the present paper, news results are reached. First, a more efficient solution of the initial linear problem is proposed. Second, always in the linear framework, the issue of describing the set of all corresponding kinematic constraints is given and reduced to the one of finding all the Lagrangian planes of a symplectic space. Third, the extension to the local non-linear case is solved. A four degree of freedom system exhibiting a maximal geometric degree of nonconservativity (s = 2) is used to illustrate our results. The issue of the global non-linear problem is not tackled. Throughout the paper, the issue of the effectiviness of the solution is systematically addressed.

Proceedings of the 2004 International Snow Science Workshop Jackson Hole Wyoming, 2004

The present study deals with snowpack motion and its interaction with a flexible snow supporting ... more The present study deals with snowpack motion and its interaction with a flexible snow supporting structure. The final aim of this research is to evaluate forces induced into a snow net system by its interaction with a snowpack. Thanks to this calculation, a better engineering design of these structures will be obtained.

Nonlinear Analysis: Real World Applications, 2016

Having recalled the kinematic structural stability (ki.s.s) issue and its solution for divergence... more Having recalled the kinematic structural stability (ki.s.s) issue and its solution for divergence-type instability, we address the same problem for flutter-type instability for the minimal required configuration of dimensions-meaning 3 degree of freedom systems. We first get a sufficient non optimal condition. In a second time, the complete issue is tackled by two different ways leading to same results. A first way using calculations on Grassmann and Stiefel manifolds that may be generalized for any dimensional configuration. A second way using the specific dimensional configuration is brought back to calculations on the sphere. Differences with divergence ki.s.s are highlighted and examples illustrate the results.

Applied Mathematical Modelling, 2015

This paper deals with both divergence and second order work criteria and the kinematical structur... more This paper deals with both divergence and second order work criteria and the kinematical structural stability called ki.s.s. In this context, kinematical structural stability means that the criterion remains valid even if the system is subjected to additional kinematic constraints. First some developments about the effect of additional kinematics constraints are presented on divergence instability. Secondly, divergence and second order work criteria are addressed. Using a variational formulation, previous results from a usual algebraic formulation using Schur's complement formula are highlighted and finally translated through the ki.s.s. concept: unconditional ki.s.s. for the second order work and the divergence of conservative systems and conditional ki.s.s. for the divergence of nonconservative elastic systems.

Un sujet unique, des compétences multiples La liste de remerciements sera longue… En effet, ce tr... more Un sujet unique, des compétences multiples La liste de remerciements sera longue… En effet, ce travail de thèse fut également le travail d'une équipe, ce qui a permis d'aborder des disciplines variées et d'exploiter des compétences multiples. Mes remerciements vont d'abord à mes encadrants : Ma directrice de thèse, Véronique Merrien-Soukatchoff, dont l'encadrement fut complet : des équations d'élasticité en anisotropie, écrites dans un train de nuit autrichien, jusqu'au pousse-pousse au bord du périphérique de Xi'an. Il me faut pareillement remercier mon co-directeur de thèse, Yann Gunzburger, « dénicheur » des Rochers de Valabres. Leurs qualités de rigueur et de précision ont, j'espère, atténué un peu mon gout de l'approximatif… merci sincèrement pour votre encadrement durant ces trois années, votre implication et votre disponibilité. Je voudrais également témoigner ma reconnaissance à l'équipe de l'INERIS : Benoit Beaufils et Clémence Dünner, dont les investissements sur le site de Valabres ont permis la réalisation de ce travail, Christophe Didier, Christian Franck et Jean-Bernard Kazmierczak, qui ont veillé au bon déroulement de la thèse et fourni un regard critique et utile à mon travail. Merci pour votre confiance, pour le soutien technique, scientifique et financier. Je voudrais pareillement remercier Suzanne Lacasse et Felix Darve, qui ont accepté d'être rapporteurs de ce travail, et à Jean-Louis Durville et Thierry Villemin, examinateurs et président du jury, pour leurs remarques constructives et le regard pertinent apporté à mon travail. Il me faut d'ailleurs préciser que ce projet de thèse a bénéficié du soutien du Ministère de l'Ecologie, de l'Energie, du Développement Durable et de l'Aménagement du Territoire au travers du programme EAT-DRS-02 de l'INERIS intitulé « Analyse, prévention et maîtrise des risques de mouvements de terrain ». Cette thèse s'est également intégrée au programme national STABROCK, financé par le Ministère de l'Equipement dans le cadre du Réseau Génie-Civil et Urbain, et qui porte sur l'étude de l'impact des changements climatiques sur la stabilité des fronts rocheux, via l'étude du site des Rochers de Valabres. Merci à Gloria Senfaute pour son enthousiasme à porter le projet et aux chercheurs et doctorants des laboratoires Géosciences Azur et Géosciences Besançon, du 3S-R de Grenoble, du LCPC et LRCPC, pour les nombreux échanges et discussions sur notre problématique commune. Je dois aussi beaucoup aux conseils de chercheurs d'horizons variés : M. Michot pour son aide en mécanique de la rupture, M. Brouand pour les analyses minéralogiques, Frantz Lahaie pour ses connaissances pointues en mesures de contraintes, Yves Gueniffey pour l'analyse de données, Judith Sausse pour l'apprentissage de la modélisation gOcad, Farid Laouafa et Alain Thoraval pour les modélisations numériques et Mountaka Souley pour sa passion de l'anisotropie transverse.. Ma reconnaissance va aussi à Mmes Schenck et Milonet pour le soin apporté aux nombreuses relectures de mes documents, et à Brigitte Siatka pour son attention quasi-maternelle apporté à ses jeunes chercheurs rêveurs. Merci également à Mme Dupont, de L'Oréal-France, et Mme D'Artois, de l'UNESCO, pour le montage du projet « Pour les femmes et la sciences ». L'obtention de cette bourse fut une expérience inoubliable : des interviews médiatiques à l'exposé de mes travaux lors d'une assemblée au siège de l'UNESCO. Outre la découverte de nouvelles disciplines, cette thèse fut l'occasion de découvrir de nouvelles contrées : Autriche, Suisse, Norvège, Russie, Chine… Merci à Isabelle Lecomte, de m'avoir invité à Oslo, pour exposer mes travaux à NORSAR et au NGI. Merci au service enseignement-recherche de TOTAL pour le financement du congrès jeunes Chercheurs à St-Petersbourg. Un grand merci également à ceux qui ont partagé mon quotidien. Tout particulièrement, mes compères de bureau : Maxime Cauvin, Diego Mercerat, Jamil Damaj, Ali Saeidi et Abdel Benouanas, qui, même s'ils ne se connaissent pas tous, garderont en mémoire les supplices affligés à notre pauvre plante verte. Merci également à mes compères de café et de RU, Philippe Lopez, Olivier Deck, Thierry Verdel, Bernard Laumonier et Christian Marignac. Enfin, merci à ma famille et à mon fiancé, dont la présence et le support furent admirables.

Natural Hazards and Earth System Sciences, 2009

Trajectory analysis models are increasingly used for rockfall hazard mapping. However, classical ... more Trajectory analysis models are increasingly used for rockfall hazard mapping. However, classical approaches only partially account for the variability of the trajectories. In this paper, a general formulation using a Taylor series expansion is proposed for the quantification of the relative importance of the different processes that explain the variability of the reflected velocity vector after bouncing. A stochastic bouncing model is obtained using a statistical analysis of a large numerical data set. Estimation is performed using hierarchical Bayesian modeling schemes. The model introduces information on the coupling of the reflected and incident velocity vectors, which satisfactorily expresses the mechanisms associated with boulder bouncing. The approach proposed is detailed in the case of the impact of a spherical boulder on a coarse soil, with special focus on the influence of soil particles' geometrical configuration near the impact point and kinematic parameters of the rock before bouncing. The results show that a first-order expansion is sufficient for the case studied and emphasize the predominant role of the local soil properties on the reflected velocity vector's variability. The proposed model is compared with classical approaches and the interest for rockfall hazard assessment of reliable stochastic bouncing models in trajectory simulations is illustrated with a simple case study.

Journal of the Mechanics and Physics of Solids, 2013

In this paper a general set of equations of motion and duality conditions to be imposed at macros... more In this paper a general set of equations of motion and duality conditions to be imposed at macroscopic surfaces of discontinuity in partially saturated, solid-second gradient porous media are derived by means of the Least Action Principle. The need of using a second gradient (of solid displacement) theory is shown to be necessary to include in the model effects related to gradients of porosity. The proposed governing equations include, in addition to balance of linear momentum for a second gradient porous continuum and to balance of water and air chemical potentials, the equations describing the evolution of solid and fluid volume fractions as supplementary independent kinematical fields. The presented equations are general in the sense that they are all written in terms of a macroscopic potential Ψ which depends on the introduced kinematical fields and on their space and time derivatives. These equations are suitable to describe the motion of a partially saturated, second gradient porous medium in the elastic and hyper-elastic regime. In the second part of the paper an additive decomposition for the potential Ψ is proposed which allows for describing some particular constitutive behaviours of the considered medium. While the potential associated to the solid matrix deformation is chosen in the form proposed by Cowin and Nunziato in [15], [33] and the potentials associated to water and air compressibility are chosen to assume a simple quadratic form, the macroscopic potentials associated to capillarity phenomena between water and air have to be derived with some additional considerations. In particular, two simple examples of microscopic distributions of water and air are considered: that of spherical bubbles and that of coalesced tubes of bubbles. Both these cases are suitable to describe capillarity phenomena in porous media which are close to the saturation state. Finally, an example of a simple microscopic distribution of water and air giving rise to a macroscopic capillary potential depending on the second gradient of fluid displacement is presented, showing the need of a further generalization of the proposed theoretical framework accounting for fluid second gradient effects.

International Journal for Numerical and Analytical Methods in Geomechanics, 2008

The bifurcation and instability conditions in geomechanics are closely related to the elasto‐plas... more The bifurcation and instability conditions in geomechanics are closely related to the elasto‐plastic behaviour. In this paper the potential of a multimechanism elasto‐plastic model to predict various modes of failure is examined. First, a brief overview for the essential aspects of the constitutive model and the development of the elasto‐plastic constitutive matrix for this model are presented. Then, numerical simulations of different drained and undrained paths in the axisymmetric and plane‐strain conditions for the Hostun sand are illustrated. These examples confirm the capacity of the model to reproduce instability and strain localization phenomena. The obtained response is in agreement with experimental observations, theoretical developments and numerical analyses existing in the literature. Copyright © 2007 John Wiley & Sons, Ltd.

Géotechnique, 2009

The Petacciato landslide that occurred between 1906 and 1966 along a stretch of the Adriatic coas... more The Petacciato landslide that occurred between 1906 and 1966 along a stretch of the Adriatic coast (Italy) and the Trevoux landslide that appeared in 1983 in France are analysed using Hill's material sufficient stability condition, which is based on the sign of the second-order work. Local and global sufficient stability criteria allow detecting and describing the instability phenomena, respectively, at the material point level and for the whole domain. By considering the non-associated Plasol elasto-plastic constitutive model and the second-order work criterion, it is shown that unstable stress–strain states can be reached in plane strain conditions, strictly inside the plastic limit criterion. The two landslides that occurred in Petacciato and Trevoux are then analysed by modelling unsaturated hydro-mechanical coupling. The analysis is carried out using the Lagamine finite element code. This original approach to slope stability analysis makes it possible successfully to exhibi...

Computers and Geotechnics, 2002

Slope stability analysis, based on the continuum mechanics assumption and finite element analysis... more Slope stability analysis, based on the continuum mechanics assumption and finite element analysis, generally uses a plasticity criterion to describe the failure mechanism. In this paper we model the failure phenomenon using a material stability criterion based on the sign of the second order work. After a brief and critical review of the classical methods for slope stability analysis, we study a case of material instability experimentally and analytically. Homogeneous stress-strain problems are then investigated ising a non-linear constitutive model. It is shown that unstable stress-strain states are reached strictly inside the plastic limit condition (set of admissible stresses). Theses analyses are then extended and applied to sandy slope problems solved by FEM.